String Class

Reference

Definition

Namespace:: System

Assembly:: System.Runtime.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

Represents text as a sequence of UTF-16 code units.

public ref class System::String sealed : IComparable, IComparable<System::String ^>, IConvertible, IEquatable<System::String ^>, System::Collections::Generic::IEnumerable<char>

public ref class System::String sealed : ICloneable, IComparable, IComparable<System::String ^>, IConvertible, IEquatable<System::String ^>, System::Collections::Generic::IEnumerable<char>

public ref class System::String sealed : ICloneable, IComparable, IComparable<System::String ^>, IConvertible, IEquatable<System::String ^>, IParsable<System::String ^>, ISpanParsable<System::String ^>, System::Collections::Generic::IEnumerable<char>

public ref class System::String sealed : ICloneable, IComparable, IConvertible, System::Collections::IEnumerable

public ref class System::String sealed : IComparable, IComparable<System::String ^>, IEquatable<System::String ^>, System::Collections::IEnumerable

public ref class System::String sealed : IComparable, IComparable<System::String ^>, IEquatable<System::String ^>, System::Collections::Generic::IEnumerable<char>

public sealed class String : IComparable, IComparable<string>, IConvertible, IEquatable<string>, System.Collections.Generic.IEnumerable<char>

public sealed class String : ICloneable, IComparable, IComparable<string>, IConvertible, IEquatable<string>, System.Collections.Generic.IEnumerable<char>

public sealed class String : ICloneable, IComparable, IComparable<string>, IConvertible, IEquatable<string>, IParsable<string>, ISpanParsable<string>, System.Collections.Generic.IEnumerable<char>

[System.Serializable]
public sealed class String : ICloneable, IComparable, IConvertible, System.Collections.IEnumerable

[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public sealed class String : ICloneable, IComparable, IComparable<string>, IConvertible, IEquatable<string>, System.Collections.Generic.IEnumerable<char>

public sealed class String : IComparable, IComparable<string>, IEquatable<string>, System.Collections.IEnumerable

public sealed class String : IComparable, IComparable<string>, IEquatable<string>, System.Collections.Generic.IEnumerable<char>

type string = class
    interface seq<char>
    interface IEnumerable
    interface IComparable
    interface IComparable<string>
    interface IConvertible
    interface IEquatable<string>

type string = class
    interface seq<char>
    interface IEnumerable
    interface ICloneable
    interface IComparable
    interface IComparable<string>
    interface IConvertible
    interface IEquatable<string>

type string = class
    interface seq<char>
    interface IEnumerable
    interface ICloneable
    interface IComparable
    interface IComparable<string>
    interface IConvertible
    interface IEquatable<string>
    interface IParsable<string>
    interface ISpanParsable<string>

type string = class
    interface seq<char>
    interface IEnumerable
    interface IComparable
    interface IComparable<string>
    interface IConvertible
    interface IEquatable<string>
    interface ICloneable

[<System.Serializable>]
type string = class
    interface IComparable
    interface ICloneable
    interface IConvertible
    interface IEnumerable

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type string = class
    interface IComparable
    interface ICloneable
    interface IConvertible
    interface IComparable<string>
    interface seq<char>
    interface IEnumerable
    interface IEquatable<string>

[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type string = class
    interface IComparable
    interface ICloneable
    interface IConvertible
    interface IEnumerable
    interface IComparable<string>
    interface seq<char>
    interface IEquatable<string>

type string = class
    interface IEnumerable
    interface IComparable
    interface IComparable<string>
    interface IEquatable<string>

type string = class
    interface IComparable
    interface IComparable<string>
    interface IEquatable<string>
    interface seq<char>
    interface IEnumerable

Public NotInheritable Class String
Implements IComparable, IComparable(Of String), IConvertible, IEnumerable(Of Char), IEquatable(Of String)

Public NotInheritable Class String
Implements ICloneable, IComparable, IComparable(Of String), IConvertible, IEnumerable(Of Char), IEquatable(Of String)

Public NotInheritable Class String
Implements ICloneable, IComparable, IComparable(Of String), IConvertible, IEnumerable(Of Char), IEquatable(Of String), IParsable(Of String), ISpanParsable(Of String)

Public NotInheritable Class String
Implements ICloneable, IComparable, IConvertible, IEnumerable

Public NotInheritable Class String
Implements IComparable, IComparable(Of String), IEnumerable, IEquatable(Of String)

Public NotInheritable Class String
Implements IComparable, IComparable(Of String), IEnumerable(Of Char), IEquatable(Of String)

Inheritance: Object
String

Attributes: SerializableAttribute ComVisibleAttribute

Implements: IEnumerable<Char> IEnumerable IComparable IComparable<String> IConvertible IEquatable<String> ICloneable IParsable<String> IParsable<TSelf> ISpanParsable<String>

Remarks

A string is a sequential collection of characters that's used to represent text. A String object is a sequential collection of System.Char objects that represent a string; a System.Char object corresponds to a UTF-16 code unit. The value of the String object is the content of the sequential collection of System.Char objects, and that value is immutable (that is, it is read-only). For more information about the immutability of strings, see the Immutability and the StringBuilder class section. The maximum size of a String object in memory is 2-GB, or about 1 billion characters.

For more information about Unicode, UTF-16, code units, code points, and the Char and Rune types, see Introduction to character encoding in .NET.

In this section:

Instantiate a String object
Char objects and Unicode characters
Strings and The Unicode Standard
Strings and embedded null characters
Strings and indexes
Null strings and empty strings
Immutability and the StringBuilder class
Ordinal vs. culture-sensitive operations
Normalization
String operations by category

Instantiate a String object

You can instantiate a String object in the following ways:

By assigning a string literal to a String variable. This is the most commonly used method for creating a string. The following example uses assignment to create several strings. Note that in C# and F#, because the backslash (\) is an escape character, literal backslashes in a string must be escaped or the entire string must be @-quoted.

using namespace System;

void main()
{
   String^ string1 = "This is a string created by assignment.";
   Console::WriteLine(string1);
   String^ string2a = "The path is C:\\PublicDocuments\\Report1.doc";
   Console::WriteLine(string2a);
}
// The example displays the following output: 
//       This is a string created by assignment. 
//       The path is C:\PublicDocuments\Report1.doc

string string1 = "This is a string created by assignment.";
Console.WriteLine(string1);
string string2a = "The path is C:\\PublicDocuments\\Report1.doc";
Console.WriteLine(string2a);
string string2b = @"The path is C:\PublicDocuments\Report1.doc";
Console.WriteLine(string2b);
// The example displays the following output:
//       This is a string created by assignment.
//       The path is C:\PublicDocuments\Report1.doc
//       The path is C:\PublicDocuments\Report1.doc

let string1 = "This is a string created by assignment."
printfn "%s" string1
let string2a = "The path is C:\\PublicDocuments\\Report1.doc"
printfn "%s" string2a
let string2b = @"The path is C:\PublicDocuments\Report1.doc"
printfn "%s" string2b
// The example displays the following output:
//       This is a string created by assignment.
//       The path is C:\PublicDocuments\Report1.doc
//       The path is C:\PublicDocuments\Report1.doc

Dim string1 As String = "This is a string created by assignment."
Console.WriteLine(string1)
Dim string2 As String = "The path is C:\PublicDocuments\Report1.doc"
Console.WriteLine(string2)
' The example displays the following output:
'       This is a string created by assignment.
'       The path is C:\PublicDocuments\Report1.doc

By calling a String class constructor. The following example instantiates strings by calling several class constructors. Note that some of the constructors include pointers to character arrays or signed byte arrays as parameters. Visual Basic does not support calls to these constructors. For detailed information about String constructors, see the String constructor summary.

using namespace System;

void main()
{
   wchar_t chars[5] = L"word";
   char bytes[6] = { 0x41, 0x42, 0x43, 0x44, 0x45, 0x00 };

   // Create a string from a character array. 
   String^ string1 = gcnew String(chars);
   Console::WriteLine(string1);

   // Create a string that consists of a character repeated 20 times. 
   String^ string2 = gcnew String('c', 20);
   Console::WriteLine(string2);

   String^ stringFromBytes = nullptr;
   String^ stringFromChars = nullptr;

   char * pbytes = &bytes[0];
   // Create a string from a pointer to a signed byte array.
   stringFromBytes = gcnew String(pbytes);

   wchar_t* pchars =  &chars[0];
   // Create a string from a pointer to a character array.
   stringFromChars = gcnew String(pchars);

   Console::WriteLine(stringFromBytes);
   Console::WriteLine(stringFromChars);
   Console::ReadLine();
}
// The example displays the following output: 
//       word 
//       cccccccccccccccccccc 
//       ABCDE 
//       word

char[] chars = { 'w', 'o', 'r', 'd' };
sbyte[] bytes = { 0x41, 0x42, 0x43, 0x44, 0x45, 0x00 };

// Create a string from a character array.
string string1 = new string(chars);
Console.WriteLine(string1);

// Create a string that consists of a character repeated 20 times.
string string2 = new string('c', 20);
Console.WriteLine(string2);

string stringFromBytes = null;
string stringFromChars = null;
unsafe
{
   fixed (sbyte* pbytes = bytes)
   {
      // Create a string from a pointer to a signed byte array.
      stringFromBytes = new string(pbytes);
   }
   fixed (char* pchars = chars)
   {
      // Create a string from a pointer to a character array.
      stringFromChars = new string(pchars);
   }
}
Console.WriteLine(stringFromBytes);
Console.WriteLine(stringFromChars);
// The example displays the following output:
//       word
//       cccccccccccccccccccc
//       ABCDE
//       word

let chars = [| 'w'; 'o'; 'r'; 'd' |]
let bytes = [| 0x41y; 0x42y; 0x43y; 0x44y; 0x45y; 0x00y |]

// Create a string from a character array.
let string1 = String chars
printfn "%s" string1

// Create a string that consists of a character repeated 20 times.
let string2 = String('c', 20)
printfn "%s" string2

let stringFromBytes =
    // Create a string from a pointer to a signed byte array.
    use pbytes = fixed bytes
    String pbytes
let stringFromChars = 
    // Create a string from a pointer to a character array.
    use pchars = fixed chars
    String pchars

printfn $"{stringFromBytes}"
printfn $"{stringFromChars}"
// The example displays the following output:
//       word
//       cccccccccccccccccccc
//       ABCDE
//       word

Dim chars() As Char = { "w"c, "o"c, "r"c, "d"c }

' Create a string from a character array.
Dim string1 As New String(chars)
Console.WriteLine(string1)

' Create a string that consists of a character repeated 20 times.
Dim string2 As New String("c"c, 20)
Console.WriteLine(string2)
' The example displays the following output:
'       word
'       cccccccccccccccccccc

By using the string concatenation operator (+ in C# and F#, and & or + in Visual Basic) to create a single string from any combination of String instances and string literals. The following example illustrates the use of the string concatenation operator.

String^ string1 = "Today is " + DateTime::Now.ToString("D") + ".";
Console::WriteLine(string1);

String^ string2 = "This is one sentence. " + "This is a second. ";
string2 += "This is a third sentence.";
Console::WriteLine(string2);
// The example displays output like the following: 
//    Today is Tuesday, July 06, 2011. 
//    This is one sentence. This is a second. This is a third sentence.

string string1 = "Today is " + DateTime.Now.ToString("D") + ".";
Console.WriteLine(string1);

string string2 = "This is one sentence. " + "This is a second. ";
string2 += "This is a third sentence.";
Console.WriteLine(string2);
// The example displays output like the following:
//    Today is Tuesday, July 06, 2011.
//    This is one sentence. This is a second. This is a third sentence.

let string1 = "Today is " + DateTime.Now.ToString("D") + "."
printfn $"{string1}"

let string2 = "This is one sentence. " + "This is a second. "
let string2 = string2 + "This is a third sentence."
printfn $"{string2}"
// The example displays output like the following:
//    Today is Tuesday, July 06, 2011.
//    This is one sentence. This is a second. This is a third sentence.

Dim string1 As String = "Today is " + Date.Now.ToString("D") + "."  
Console.WriteLine(string1)
Dim string2 As String = "This is one sentence. " + "This is a second. "
string2 += "This is a third sentence."
Console.WriteLine(string2)      
' The example displays output like the following:
'    Today is Tuesday, July 06, 2011.
'    This is one sentence. This is a second. This is a third sentence.

By retrieving a property or calling a method that returns a string. The following example uses the methods of the String class to extract a substring from a larger string.

String^ sentence = "This sentence has five words.";
// Extract the second word.
int startPosition = sentence->IndexOf(" ") + 1;
String^ word2 = sentence->Substring(startPosition, 
                                    sentence->IndexOf(" ", startPosition) - startPosition);
Console::WriteLine("Second word: " + word2);

string sentence = "This sentence has five words.";
// Extract the second word.
int startPosition = sentence.IndexOf(" ") + 1;
string word2 = sentence.Substring(startPosition,
                                  sentence.IndexOf(" ", startPosition) - startPosition);
Console.WriteLine("Second word: " + word2);
// The example displays the following output:
//       Second word: sentence

let sentence = "This sentence has five words."
// Extract the second word.
let startPosition = sentence.IndexOf " " + 1
let word2 = 
    sentence.Substring(startPosition, sentence.IndexOf(" ", startPosition) - startPosition)
printfn $"Second word: {word2}"
// The example displays the following output:
//       Second word: sentence

Dim sentence As String = "This sentence has five words."
' Extract the second word.
Dim startPosition As Integer = sentence.IndexOf(" ") + 1
Dim word2 As String = sentence.Substring(startPosition, 
                                         sentence.IndexOf(" ", startPosition) - startPosition) 
Console.WriteLine("Second word: " + word2)
' The example displays the following output:
'       Second word: sentence

By calling a formatting method to convert a value or object to its string representation. The following example uses the composite formatting feature to embed the string representation of two objects into a string.

DateTime^ dateAndTime = gcnew DateTime(2011, 7, 6, 7, 32, 0);
Double temperature = 68.3;
String^ result = String::Format("At {0:t} on {0:D}, the temperature was {1:F1} degrees Fahrenheit.",
                               dateAndTime, temperature);
Console::WriteLine(result);
// The example displays the following output: 
//       At 7:32 AM on Wednesday, July 06, 2011, the temperature was 68.3 degrees Fahrenheit.

DateTime dateAndTime = new DateTime(2011, 7, 6, 7, 32, 0);
double temperature = 68.3;
string result = String.Format("At {0:t} on {0:D}, the temperature was {1:F1} degrees Fahrenheit.",
                              dateAndTime, temperature);
Console.WriteLine(result);
// The example displays the following output:
//       At 7:32 AM on Wednesday, July 06, 2011, the temperature was 68.3 degrees Fahrenheit.

let dateAndTime = DateTime(2011, 7, 6, 7, 32, 0)
let temperature = 68.3
String.Format("At {0:t} on {0:D}, the temperature was {1:F1} degrees Fahrenheit.", dateAndTime, temperature)
|> printfn "%s"
// The example displays the following output:
//       At 7:32 AM on Wednesday, July 06, 2011, the temperature was 68.3 degrees Fahrenheit.

Dim dateAndTime As DateTime = #07/06/2011 7:32:00AM#
Dim temperature As Double = 68.3
Dim result As String = String.Format("At {0:t} on {0:D}, the temperature was {1:F1} degrees Fahrenheit.",
                                     dateAndTime, temperature)
Console.WriteLine(result)
' The example displays the following output:
'       At 7:32 AM on Wednesday, July 06, 2011, the temperature was 68.3 degrees Fahrenheit.

Char objects and Unicode characters

Each character in a string is defined by a Unicode scalar value, also called a Unicode code point or the ordinal (numeric) value of the Unicode character. Each code point is encoded by using UTF-16 encoding, and the numeric value of each element of the encoding is represented by a Char object.

Note

Note that, because a String instance consists of a sequential collection of UTF-16 code units, it is possible to create a String object that is not a well-formed Unicode string. For example, it is possible to create a string that has a low surrogate without a corresponding high surrogate. Although some methods, such as the methods of encoding and decoding objects in the System.Text namespace, may performs checks to ensure that strings are well-formed, String class members don't ensure that a string is well-formed.

A single Char object usually represents a single code point; that is, the numeric value of the Char equals the code point. For example, the code point for the character "a" is U+0061. However, a code point might require more than one encoded element (more than one Char object). The Unicode standard defines two types of characters that correspond to multiple Char objects: graphemes, and Unicode supplementary code points that correspond to characters in the Unicode supplementary planes.

A grapheme is represented by a base character followed by one or more combining characters. For example, the character ä is represented by a Char object whose code point is U+0061 followed by a Char object whose code point is U+0308. This character can also be defined by a single Char object that has a code point of U+00E4. As the following example shows, a culture-sensitive comparison for equality indicates that these two representations are equal, although an ordinary ordinal comparison does not. However, if the two strings are normalized, an ordinal comparison also indicates that they are equal. (For more information on normalizing strings, see the Normalization section.)

using namespace System;
using namespace System::Globalization;
using namespace System::IO;

void main()
{
   StreamWriter^ sw = gcnew StreamWriter(".\\graphemes.txt");
   String^ grapheme = L"a" + L"\u0308";
   sw->WriteLine(grapheme);

   String^ singleChar = "\u00e4";
   sw->WriteLine(singleChar);

   sw->WriteLine("{0} = {1} (Culture-sensitive): {2}", grapheme, singleChar, 
                  String::Equals(grapheme, singleChar, 
                              StringComparison::CurrentCulture));
   sw->WriteLine("{0} = {1} (Ordinal): {2}", grapheme, singleChar, 
                  String::Equals(grapheme, singleChar, 
                              StringComparison::Ordinal));
   sw->WriteLine("{0} = {1} (Normalized Ordinal): {2}", grapheme, singleChar, 
                  String::Equals(grapheme->Normalize(), 
                              singleChar->Normalize(), 
                              StringComparison::Ordinal));
   sw->Close(); 
}
// The example produces the following output: 
//       ä 
//       ä 
//       ä = ä (Culture-sensitive): True 
//       ä = ä (Ordinal): False 
//       ä = ä (Normalized Ordinal): True

using System;
using System.Globalization;
using System.IO;

public class Example
{
   public static void Main()
   {
      StreamWriter sw = new StreamWriter(@".\graphemes.txt");
      string grapheme = "\u0061\u0308";
      sw.WriteLine(grapheme);
      
      string singleChar = "\u00e4";
      sw.WriteLine(singleChar);
            
      sw.WriteLine("{0} = {1} (Culture-sensitive): {2}", grapheme, singleChar, 
                   String.Equals(grapheme, singleChar, 
                                 StringComparison.CurrentCulture));
      sw.WriteLine("{0} = {1} (Ordinal): {2}", grapheme, singleChar, 
                   String.Equals(grapheme, singleChar, 
                                 StringComparison.Ordinal));
      sw.WriteLine("{0} = {1} (Normalized Ordinal): {2}", grapheme, singleChar, 
                   String.Equals(grapheme.Normalize(), 
                                 singleChar.Normalize(), 
                                 StringComparison.Ordinal));
      sw.Close(); 
   }
}
// The example produces the following output:
//       ä
//       ä
//       ä = ä (Culture-sensitive): True
//       ä = ä (Ordinal): False
//       ä = ä (Normalized Ordinal): True

open System
open System.IO

do
    use sw = new StreamWriter(@".\graphemes.txt")
    let grapheme = "\u0061\u0308"
    sw.WriteLine grapheme

    let singleChar = "\u00e4"
    sw.WriteLine singleChar

    sw.WriteLine("{0} = {1} (Culture-sensitive): {2}", grapheme, singleChar, 
                String.Equals(grapheme, singleChar,
                                StringComparison.CurrentCulture))
    sw.WriteLine("{0} = {1} (Ordinal): {2}", grapheme, singleChar,
                String.Equals(grapheme, singleChar,
                                StringComparison.Ordinal))
    sw.WriteLine("{0} = {1} (Normalized Ordinal): {2}", grapheme, singleChar,
                String.Equals(grapheme.Normalize(),
                                singleChar.Normalize(),
                                StringComparison.Ordinal))
// The example produces the following output:
//       ä
//       ä
//       ä = ä (Culture-sensitive): True
//       ä = ä (Ordinal): False
//       ä = ä (Normalized Ordinal): True

Imports System.Globalization
Imports System.IO

Module Example
   Public Sub Main()
      Dim sw As New StreamWriter(".\graphemes.txt")
      Dim grapheme As String = ChrW(&H0061) + ChrW(&h0308)
      sw.WriteLine(grapheme)
      
      Dim singleChar As String = ChrW(&h00e4)
      sw.WriteLine(singleChar)
            
      sw.WriteLine("{0} = {1} (Culture-sensitive): {2}", grapheme, singleChar, 
                   String.Equals(grapheme, singleChar, 
                                 StringComparison.CurrentCulture))
      sw.WriteLine("{0} = {1} (Ordinal): {2}", grapheme, singleChar, 
                   String.Equals(grapheme, singleChar, 
                                 StringComparison.Ordinal))
      sw.WriteLine("{0} = {1} (Normalized Ordinal): {2}", grapheme, singleChar, 
                   String.Equals(grapheme.Normalize(), 
                                 singleChar.Normalize(), 
                                 StringComparison.Ordinal))
      sw.Close() 
   End Sub
End Module
' The example produces the following output:
'       ä
'       ä
'       ä = ä (Culture-sensitive): True
'       ä = ä (Ordinal): False
'       ä = ä (Normalized Ordinal): True

A Unicode supplementary code point (a surrogate pair) is represented by a Char object whose code point is a high surrogate followed by a Char object whose code point is a low surrogate. The code units of high surrogates range from U+D800 to U+DBFF. The code units of low surrogates range from U+DC00 to U+DFFF. Surrogate pairs are used to represent characters in the 16 Unicode supplementary planes. The following example creates a surrogate character and passes it to the Char.IsSurrogatePair(Char, Char) method to determine whether it is a surrogate pair.

using namespace System;

void main()
{
   String^ surrogate =  L"\xD800\xDC03" ;
   for (int ctr = 0; ctr < surrogate->Length; ctr++)
      Console::Write("U+{0:X4} ", Convert::ToUInt16(surrogate[ctr]));

   Console::WriteLine();
   Console::WriteLine("   Is Surrogate Pair: {0}", 
                      Char::IsSurrogatePair(surrogate[0], surrogate[1]));
   Console::ReadLine();
}
// The example displays the following output: 
//       U+D800 U+DC03 
//          Is Surrogate Pair: True

string surrogate = "\uD800\uDC03";
for (int ctr = 0; ctr < surrogate.Length; ctr++) 
   Console.Write($"U+{(ushort)surrogate[ctr]:X2} ");

Console.WriteLine();
Console.WriteLine("   Is Surrogate Pair: {0}", 
                  Char.IsSurrogatePair(surrogate[0], surrogate[1]));
// The example displays the following output:
//       U+D800 U+DC03
//          Is Surrogate Pair: True

open System

let surrogate = "\uD800\uDC03"
for i = 0 to surrogate.Length - 1 do
    printf $"U+{uint16 surrogate[i]:X2} "

printfn $"\n   Is Surrogate Pair: {Char.IsSurrogatePair(surrogate[0], surrogate[1])}"
// The example displays the following output:
//       U+D800 U+DC03
//          Is Surrogate Pair: True

Module Example
   Public Sub Main()
      Dim surrogate As String = ChrW(&hD800) + ChrW(&hDC03)
      For ctr As Integer = 0 To surrogate.Length - 1
         Console.Write("U+{0:X2} ", Convert.ToUInt16(surrogate(ctr)))
      Next   
      Console.WriteLine()
      Console.WriteLine("   Is Surrogate Pair: {0}", 
                        Char.IsSurrogatePair(surrogate(0), surrogate(1)))
   End Sub
End Module

' The example displays the following output:
'       U+D800 U+DC03
'          Is Surrogate Pair: True

Strings and the Unicode Standard

Characters in a string are represented by UTF-16 encoded code units, which correspond to Char values.

Each character in a string has an associated Unicode character category, which is represented in .NET by the UnicodeCategory enumeration. The category of a character or a surrogate pair can be determined by calling the CharUnicodeInfo.GetUnicodeCategory method.

.NET maintains its own table of characters and their corresponding categories, which ensures that a specific version of a .NET implementation running on different platforms returns identical character category information. On all .NET versions and across all OS platforms, character category information is provided by the Unicode Character Database.

The following table lists .NET versions and the versions of the Unicode Standard on which their character categories are based.

.NET version	Version of the Unicode Standard
.NET Framework 1.1	The Unicode Standard, Version 4.0.0
.NET Framework 2.0	The Unicode Standard, Version 5.0.0
.NET Framework 3.5	The Unicode Standard, Version 5.0.0
.NET Framework 4	The Unicode Standard, Version 5.0.0
.NET Framework 4.5	The Unicode Standard, Version 6.3.0
.NET Framework 4.5.1	The Unicode Standard, Version 6.3.0
.NET Framework 4.5.2	The Unicode Standard, Version 6.3.0
.NET Framework 4.6	The Unicode Standard, Version 6.3.0
.NET Framework 4.6.1	The Unicode Standard, Version 6.3.0
.NET Framework 4.6.2 and later versions	The Unicode Standard, Version 8.0.0
.NET Core 2.1	The Unicode Standard, Version 8.0.0
.NET Core 3.1	The Unicode Standard, Version 11.0.0
.NET 5	The Unicode Standard, Version 13.0.0

In addition, .NET supports string comparison and sorting based on the Unicode standard. .NET Framework 4 and previous versions maintain their own table of string data. This is also true of versions of .NET Framework starting with .NET Framework 4.5 running on Windows 7. Starting with .NET Framework 4.5 running on Windows 8 and later versions of the Windows operating system, the runtime delegates string comparison and sorting operations to the operating system. On .NET Core and .NET 5+, string comparison and sorting information is provided by International Components for Unicode libraries (except on Windows versions prior to Windows 10 May 2019 Update). The following table lists the versions of .NET and the versions of the Unicode Standard on which character comparison and sorting are based.

.NET version	Version of the Unicode Standard
.NET Framework 1.1	The Unicode Standard, Version 4.0.0
.NET Framework 2.0	The Unicode Standard, Version 5.0.0
.NET Framework 3.5	The Unicode Standard, Version 5.0.0
.NET Framework 4	The Unicode Standard, Version 5.0.0
.NET Framework 4.5 and later on Windows 7	The Unicode Standard, Version 5.0.0
.NET Framework 4.5 and later on Windows 8 and later Windows operating systems	The Unicode Standard, Version 6.3.0
.NET Core and .NET 5+	Depends on the version of the Unicode Standard supported by the underlying operating system.

Strings and embedded null characters

In .NET, a String object can include embedded null characters, which count as a part of the string's length. However, in some languages such as C and C++, a null character indicates the end of a string; it is not considered a part of the string and is not counted as part of the string's length. This means that the following common assumptions that C and C++ programmers or libraries written in C or C++ might make about strings are not necessarily valid when applied to String objects:

The value returned by the strlen or wcslen functions does not necessarily equal String.Length.
The string created by the strcpy_s or wcscpy_s functions is not necessarily identical to the string created by the String.Copy method.

You should ensure that native C and C++ code that instantiates String objects, and code that is passed String objects through platform invoke, don't assume that an embedded null character marks the end of the string.

Embedded null characters in a string are also treated differently when a string is sorted (or compared) and when a string is searched. Null characters are ignored when performing culture-sensitive comparisons between two strings, including comparisons using the invariant culture. They are considered only for ordinal or case-insensitive ordinal comparisons. On the other hand, embedded null characters are always considered when searching a string with methods such as Contains, StartsWith, and IndexOf.

Strings and indexes

An index is the position of a Char object (not a Unicode character) in a String. An index is a zero-based, nonnegative number that starts from the first position in the string, which is index position zero. A number of search methods, such as IndexOf and LastIndexOf, return the index of a character or substring in the string instance.

The Chars[] property lets you access individual Char objects by their index position in the string. Because the Chars[] property is the default property (in Visual Basic) or the indexer (in C# and F#), you can access the individual Char objects in a string by using code such as the following. This code looks for white space or punctuation characters in a string to determine how many words the string contains.

using namespace System;

void main()
{
   String^ s1 = "This string consists of a single short sentence.";
   int nWords = 0;

   s1 = s1->Trim();      
   for (int ctr = 0; ctr < s1->Length; ctr++) {
         if (Char::IsPunctuation(s1[ctr]) | Char::IsWhiteSpace(s1[ctr]))
            nWords++;              
   }
   Console::WriteLine("The sentence\n   {0}\nhas {1} words.",
                     s1, nWords);           
}
// The example displays the following output: 
//       The sentence 
//          This string consists of a single short sentence. 
//       has 8 words.

string s1 = "This string consists of a single short sentence.";
int nWords = 0;

s1 = s1.Trim();      
for (int ctr = 0; ctr < s1.Length; ctr++) {
   if (Char.IsPunctuation(s1[ctr]) | Char.IsWhiteSpace(s1[ctr]))
      nWords++;              
}
Console.WriteLine("The sentence\n   {0}\nhas {1} words.",
                  s1, nWords);                                                                     
// The example displays the following output:
//       The sentence
//          This string consists of a single short sentence.
//       has 8 words.

let s1 = "This string consists of a single short sentence."
let mutable nWords = 0

for i = 0 to s1.Length - 1 do
    if Char.IsPunctuation s1[i] || Char.IsWhiteSpace s1[i] then
        nWords <- nWords + 1
printfn $"The sentence\n   {s1}\nhas {nWords} words."
// The example displays the following output:
//       The sentence
//          This string consists of a single short sentence.
//       has 8 words.

Module Example
   Public Sub Main()
      Dim s1 As String = "This string consists of a single short sentence."
      Dim nWords As Integer = 0

      s1 = s1.Trim()      
      For ctr As Integer = 0 To s1.Length - 1
         If Char.IsPunctuation(s1(ctr)) Or Char.IsWhiteSpace(s1(ctr)) 
            nWords += 1              
         End If   
      Next
      Console.WriteLine("The sentence{2}   {0}{2}has {1} words.",
                        s1, nWords, vbCrLf)                                                                     
   End Sub
End Module
' The example displays the following output:
'       The sentence
'          This string consists of a single short sentence.
'       has 8 words.

Because the String class implements the IEnumerable interface, you can also iterate through the Char objects in a string by using a foreach construct, as the following example shows.

using namespace System;

void main()
{
   String^ s1 = "This string consists of a single short sentence.";
   int nWords = 0;

   s1 = s1->Trim();      
   for each (Char ch in s1)
   {
      if (Char::IsPunctuation(ch) | Char::IsWhiteSpace(ch))
         nWords++;              
   }
   Console::WriteLine("The sentence\n   {0}\nhas {1} words.",
                      s1, nWords);  
   Console::ReadLine();
}
// The example displays the following output: 
//       The sentence 
//          This string consists of a single short sentence. 
//       has 8 words.

string s1 = "This string consists of a single short sentence.";
int nWords = 0;

s1 = s1.Trim();      
foreach (var ch in s1) {
   if (Char.IsPunctuation(ch) | Char.IsWhiteSpace(ch))
      nWords++;              
}
Console.WriteLine("The sentence\n   {0}\nhas {1} words.",
                  s1, nWords);                                                                     
// The example displays the following output:
//       The sentence
//          This string consists of a single short sentence.
//       has 8 words.

let s1 = "This string consists of a single short sentence."
let mutable nWords = 0

for ch in s1 do
    if Char.IsPunctuation ch || Char.IsWhiteSpace ch then
        nWords <- nWords + 1
printfn $"The sentence\n   {s1}\nhas {nWords} words."
// The example displays the following output:
//       The sentence
//          This string consists of a single short sentence.
//       has 8 words.

Module Example
   Public Sub Main()
      Dim s1 As String = "This string consists of a single short sentence."
      Dim nWords As Integer = 0

      s1 = s1.Trim()      
      For Each ch In s1
         If Char.IsPunctuation(ch) Or Char.IsWhiteSpace(ch) Then 
            nWords += 1              
         End If   
      Next
      Console.WriteLine("The sentence{2}   {0}{2}has {1} words.",
                        s1, nWords, vbCrLf)                                                                     
   End Sub
End Module
' The example displays the following output:
'       The sentence
'          This string consists of a single short sentence.
'       has 8 words.

Consecutive index values might not correspond to consecutive Unicode characters, because a Unicode character might be encoded as more than one Char object. In particular, a string may contain multi-character units of text that are formed by a base character followed by one or more combining characters or by surrogate pairs. To work with Unicode characters instead of Char objects, use the System.Globalization.StringInfo and TextElementEnumerator classes, or the String.EnumerateRunes method and the Rune struct. The following example illustrates the difference between code that works with Char objects and code that works with Unicode characters. It compares the number of characters or text elements in each word of a sentence. The string includes two sequences of a base character followed by a combining character.

using namespace System;
using namespace System::Collections::Generic;
using namespace System::Globalization;

void main()
{
   // First sentence of The Mystery of the Yellow Room, by Leroux. 
   String^ opening = L"Ce n'est pas sans une certaine émotion que "+
                     L"je commence à raconter ici les aventures " +
                     L"extraordinaires de Joseph Rouletabille."; 
  
   // Character counters. 
   int nChars = 0;
   // Objects to store word count.
   List<int>^ chars = gcnew List<int>();
   List<int>^ elements = gcnew List<int>();

   for each (Char ch in opening) {
      // Skip the ' character. 
      if (ch == '\x0027') continue;

      if (Char::IsWhiteSpace(ch) | (Char::IsPunctuation(ch))) {
         chars->Add(nChars);
         nChars = 0;
      }
      else {
         nChars++;
      }
   }

   TextElementEnumerator^ te = StringInfo::GetTextElementEnumerator(opening);
   while (te->MoveNext()) {
      String^ s = te->GetTextElement();   
      // Skip the ' character. 
      if (s == "\x0027") continue;
      if ( String::IsNullOrEmpty(s->Trim()) | (s->Length == 1 && Char::IsPunctuation(Convert::ToChar(s)))) {
         elements->Add(nChars);         
         nChars = 0;
      }
      else {
         nChars++;
      }
   }

   // Display character counts.
   Console::WriteLine("{0,6} {1,20} {2,20}",
                      "Word #", "Char Objects", "Characters"); 
   for (int ctr = 0; ctr < chars->Count; ctr++) 
      Console::WriteLine("{0,6} {1,20} {2,20}",
                         ctr, chars[ctr], elements[ctr]); 
   Console::ReadLine();
}
// The example displays the following output:
//      Word #         Char Objects           Characters
//           0                    2                    2
//           1                    4                    4
//           2                    3                    3
//           3                    4                    4
//           4                    3                    3
//           5                    8                    8
//           6                    8                    7
//           7                    3                    3
//           8                    2                    2
//           9                    8                    8
//          10                    2                    1
//          11                    8                    8
//          12                    3                    3
//          13                    3                    3
//          14                    9                    9
//          15                   15                   15
//          16                    2                    2
//          17                    6                    6
//          18                   12                   12

// First sentence of The Mystery of the Yellow Room, by Leroux.
string opening = "Ce n'est pas sans une certaine émotion que "+
                 "je commence à raconter ici les aventures " +
                 "extraordinaires de Joseph Rouletabille."; 
// Character counters.
int nChars = 0;
// Objects to store word count.
List<int> chars = new List<int>();
List<int> elements = new List<int>();

foreach (var ch in opening) {
   // Skip the ' character.
   if (ch == '\u0027') continue;
        
   if (Char.IsWhiteSpace(ch) | (Char.IsPunctuation(ch))) {
      chars.Add(nChars);
      nChars = 0;
   }
   else {
      nChars++;
   }
}

System.Globalization.TextElementEnumerator te = 
   System.Globalization.StringInfo.GetTextElementEnumerator(opening);
while (te.MoveNext()) {
   string s = te.GetTextElement();   
   // Skip the ' character.
   if (s == "\u0027") continue;
   if ( String.IsNullOrEmpty(s.Trim()) | (s.Length == 1 && Char.IsPunctuation(Convert.ToChar(s)))) {
      elements.Add(nChars);         
      nChars = 0;
   }
   else {
      nChars++;
   }
}

// Display character counts.
Console.WriteLine("{0,6} {1,20} {2,20}",
                  "Word #", "Char Objects", "Characters"); 
for (int ctr = 0; ctr < chars.Count; ctr++) 
   Console.WriteLine("{0,6} {1,20} {2,20}",
                     ctr, chars[ctr], elements[ctr]); 
// The example displays the following output:
//       Word #         Char Objects           Characters
//            0                    2                    2
//            1                    4                    4
//            2                    3                    3
//            3                    4                    4
//            4                    3                    3
//            5                    8                    8
//            6                    8                    7
//            7                    3                    3
//            8                    2                    2
//            9                    8                    8
//           10                    2                    1
//           11                    8                    8
//           12                    3                    3
//           13                    3                    3
//           14                    9                    9
//           15                   15                   15
//           16                    2                    2
//           17                    6                    6
//           18                   12                   12

open System
open System.Globalization

// First sentence of The Mystery of the Yellow Room, by Leroux.
let opening = "Ce n'est pas sans une certaine émotion que je commence à raconter ici les aventures extraordinaires de Joseph Rouletabille."
// Character counters.
let mutable nChars = 0
// Objects to store word count.
let chars = ResizeArray<int>()
let elements = ResizeArray<int>()

for ch in opening do
    // Skip the ' character.
    if ch <> '\u0027' then
        if Char.IsWhiteSpace ch || Char.IsPunctuation ch then
            chars.Add nChars
            nChars <- 0
        else
            nChars <- nChars + 1

let te = StringInfo.GetTextElementEnumerator opening
while te.MoveNext() do
    let s = te.GetTextElement()
    // Skip the ' character.
    if s <> "\u0027" then
        if String.IsNullOrEmpty(s.Trim()) || (s.Length = 1 && Char.IsPunctuation(Convert.ToChar s)) then
            elements.Add nChars
            nChars <- 0
        else
            nChars <- nChars + 1

// Display character counts.
printfn "%6s %20s %20s" "Word #" "Char Objects " "Characters"
for i = 0 to chars.Count - 1 do
    printfn "%6d %20d %20d" i chars[i] elements[i]
// The example displays the following output:
//       Word #         Char Objects           Characters
//            0                    2                    2
//            1                    4                    4
//            2                    3                    3
//            3                    4                    4
//            4                    3                    3
//            5                    8                    8
//            6                    8                    7
//            7                    3                    3
//            8                    2                    2
//            9                    8                    8
//           10                    2                    1
//           11                    8                    8
//           12                    3                    3
//           13                    3                    3
//           14                    9                    9
//           15                   15                   15
//           16                    2                    2
//           17                    6                    6
//           18                   12                   12

Imports System.Collections.Generic
Imports System.Globalization

Module Example
   Public Sub Main()
      ' First sentence of The Mystery of the Yellow Room, by Leroux.
      Dim opening As String = "Ce n'est pas sans une certaine émotion que "+
                              "je commence à raconter ici les aventures " +
                              "extraordinaires de Joseph Rouletabille." 
      ' Character counters.
      Dim nChars As Integer = 0
      ' Objects to store word count.
      Dim chars As New List(Of Integer)()
      Dim elements As New List(Of Integer)()
      
      For Each ch In opening
         ' Skip the ' character.
         If ch = ChrW(&h0027) Then Continue For
              
         If Char.IsWhiteSpace(ch) Or Char.IsPunctuation(ch) Then
            chars.Add(nChars)
            nChars = 0
         Else 
            nChars += 1
         End If
      Next

      Dim te As TextElementEnumerator = StringInfo.GetTextElementEnumerator(opening)
      Do While te.MoveNext()
         Dim s As String = te.GetTextElement()   
         ' Skip the ' character.
         If s = ChrW(&h0027) Then Continue Do
         If String.IsNullOrEmpty(s.Trim()) Or (s.Length = 1 AndAlso Char.IsPunctuation(Convert.ToChar(s))) 
            elements.Add(nChars)         
            nChars = 0
         Else 
            nChars += 1
         End If
      Loop

      ' Display character counts.
      Console.WriteLine("{0,6} {1,20} {2,20}",
                        "Word #", "Char Objects", "Characters") 
      For ctr As Integer = 0 To chars.Count - 1 
         Console.WriteLine("{0,6} {1,20} {2,20}",
                           ctr, chars(ctr), elements(ctr)) 
      Next                        
   End Sub
End Module
' The example displays the following output:
'    Word #         Char Objects           Characters
'         0                    2                    2
'         1                    4                    4
'         2                    3                    3
'         3                    4                    4
'         4                    3                    3
'         5                    8                    8
'         6                    8                    7
'         7                    3                    3
'         8                    2                    2
'         9                    8                    8
'        10                    2                    1
'        11                    8                    8
'        12                    3                    3
'        13                    3                    3
'        14                    9                    9
'        15                   15                   15
'        16                    2                    2
'        17                    6                    6
'        18                   12                   12

This example works with text elements by using the StringInfo.GetTextElementEnumerator method and the TextElementEnumerator class to enumerate all the text elements in a string. You can also retrieve an array that contains the starting index of each text element by calling the StringInfo.ParseCombiningCharacters method.

For more information about working with units of text rather than individual Char values, see Introduction to character encoding in .NET.

Null strings and empty strings

A string that has been declared but has not been assigned a value is null. Attempting to call methods on that string throws a NullReferenceException. A null string is different from an empty string, which is a string whose value is "" or String.Empty. In some cases, passing either a null string or an empty string as an argument in a method call throws an exception. For example, passing a null string to the Int32.Parse method throws an ArgumentNullException, and passing an empty string throws a FormatException. In other cases, a method argument can be either a null string or an empty string. For example, if you are providing an IFormattable implementation for a class, you want to equate both a null string and an empty string with the general ("G") format specifier.

The String class includes the following two convenience methods that enable you to test whether a string is null or empty:

IsNullOrEmpty, which indicates whether a string is either null or is equal to String.Empty. This method eliminates the need to use code such as the following:

if (str == nullptr || str->Equals(String::Empty))

if (str == null || str.Equals(String.Empty))

if str = null || str.Equals String.Empty then

If str Is Nothing OrElse str.Equals(String.Empty) Then

IsNullOrWhiteSpace, which indicates whether a string is null, equals String.Empty, or consists exclusively of white-space characters. This method eliminates the need to use code such as the following:

if (str == nullptr || str->Equals(String::Empty) || str->Trim()->Equals(String::Empty))

if (str == null || str.Equals(String.Empty) || str.Trim().Equals(String.Empty))

if str = null || str.Equals String.Empty || str.Trim().Equals String.Empty then

If str Is Nothing OrElse str.Equals(String.Empty) OrElse str.Trim().Equals(String.Empty)

The following example uses the IsNullOrEmpty method in the IFormattable.ToString implementation of a custom Temperature class. The method supports the "G", "C", "F", and "K" format strings. If an empty format string or a format string whose value is null is passed to the method, its value is changed to the "G" format string.

public:
   virtual String^ ToString(String^ format, IFormatProvider^ provider) 
   {
      if (String::IsNullOrEmpty(format)) format = "G";  
      if (provider == nullptr) provider = CultureInfo::CurrentCulture;
      
      switch (Convert::ToUInt16(format->ToUpperInvariant()))
      {
         // Return degrees in Celsius.    
         case 'G':
         case 'C':
            return temp.ToString("F2", provider) + L"�C";
         // Return degrees in Fahrenheit.
         case 'F': 
            return (temp * 9 / 5 + 32).ToString("F2", provider) + L"�F";
         // Return degrees in Kelvin.
         case 'K':   
            return (temp + 273.15).ToString();
         default:
            throw gcnew FormatException(
                  String::Format("The {0} format string is not supported.", 
                                 format));
      }                                   
   }

public string ToString(string format, IFormatProvider provider) 
{
   if (String.IsNullOrEmpty(format)) format = "G";  
   if (provider == null) provider = CultureInfo.CurrentCulture;
   
   switch (format.ToUpperInvariant())
   {
      // Return degrees in Celsius.    
      case "G":
      case "C":
         return temp.ToString("F2", provider) + "°C";
      // Return degrees in Fahrenheit.
      case "F": 
         return (temp * 9 / 5 + 32).ToString("F2", provider) + "°F";
      // Return degrees in Kelvin.
      case "K":   
         return (temp + 273.15).ToString();
      default:
         throw new FormatException(
               String.Format("The {0} format string is not supported.", 
                             format));
   }                                   
}

member _.ToString(format: string, provider: IFormatProvider) =
    let format = 
        if String.IsNullOrEmpty format then "G" else format
    
    let provider: IFormatProvider = 
        if provider = null then CultureInfo.CurrentCulture else provider

    match format.ToUpperInvariant() with
    // Return degrees in Celsius.
    | "G"
    | "C" ->
        temp.ToString("F2", provider) + "°C"
    // Return degrees in Fahrenheit.
    | "F" ->
        (temp * 9. / 5. + 32.).ToString("F2", provider) + "°F"
    // Return degrees in Kelvin.
    | "K" ->
        (temp + 273.15).ToString()
    | _ ->
        raise (FormatException(String.Format("The {0} format string is not supported.",format)))

Public Overloads Function ToString(fmt As String, provider As IFormatProvider) As String _
                Implements IFormattable.ToString
   If String.IsNullOrEmpty(fmt) Then fmt = "G"  
   If provider Is Nothing Then provider = CultureInfo.CurrentCulture
   
   Select Case fmt.ToUpperInvariant()
      ' Return degrees in Celsius.    
      Case "G", "C"
         Return temp.ToString("F2", provider) + "°C"
      ' Return degrees in Fahrenheit.
      Case "F" 
         Return (temp * 9 / 5 + 32).ToString("F2", provider) + "°F"
      ' Return degrees in Kelvin.
      Case "K"   
         Return (temp + 273.15).ToString()
      Case Else
         Throw New FormatException(
               String.Format("The {0} format string is not supported.", 
                             fmt))
    End Select                                   
End Function

Immutability and the StringBuilder class

A String object is called immutable (read-only), because its value cannot be modified after it has been created. Methods that appear to modify a String object actually return a new String object that contains the modification.

Because strings are immutable, string manipulation routines that perform repeated additions or deletions to what appears to be a single string can exact a significant performance penalty. For example, the following code uses a random number generator to create a string with 1000 characters in the range 0x0001 to 0x052F. Although the code appears to use string concatenation to append a new character to the existing string named str, it actually creates a new String object for each concatenation operation.

using namespace System;
using namespace System::IO;
using namespace System::Text;

void main()
{
   Random^ rnd = gcnew Random();

   String^ str = String::Empty;
   StreamWriter^ sw = gcnew StreamWriter(".\\StringFile.txt", 
                        false, Encoding::Unicode);

   for (int ctr = 0; ctr <= 1000; ctr++) {
      str += Convert::ToChar(rnd->Next(1, 0x0530)); 
      if (str->Length % 60 == 0)
         str += Environment::NewLine;          
   }                    
   sw->Write(str);
   sw->Close();
}

using System;
using System.IO;
using System.Text;

public class Example
{
   public static void Main()
   {
      Random rnd = new Random();
      
      string str = String.Empty;
      StreamWriter sw = new StreamWriter(@".\StringFile.txt", 
                           false, Encoding.Unicode);

      for (int ctr = 0; ctr <= 1000; ctr++) {
         str += (char)rnd.Next(1, 0x0530);
         if (str.Length % 60 == 0)
            str += Environment.NewLine;          
      }                    
      sw.Write(str);
      sw.Close();
   }
}

open System
open System.IO
open System.Text

do
    let rnd = Random()

    let mutable str = String.Empty
    use sw = new StreamWriter(@".\StringFile.txt", false, Encoding.Unicode)
    for _ = 0 to 1000 do
        str <- str + (rnd.Next(1, 0x0530) |> char |> string)
        if str.Length % 60 = 0 then
            str <- str + Environment.NewLine
    sw.Write str

Imports System.IO
Imports System.Text

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      
      Dim str As String = String.Empty
      Dim sw As New StreamWriter(".\StringFile.txt", 
                           False, Encoding.Unicode)

      For ctr As Integer = 0 To 1000
         str += ChrW(rnd.Next(1, &h0530)) 
         If str.Length Mod 60 = 0 Then str += vbCrLf          
      Next                    
      sw.Write(str)
      sw.Close()
   End Sub
End Module

You can use the StringBuilder class instead of the String class for operations that make multiple changes to the value of a string. Unlike instances of the String class, StringBuilder objects are mutable; when you concatenate, append, or delete substrings from a string, the operations are performed on a single string. When you have finished modifying the value of a StringBuilder object, you can call its StringBuilder.ToString method to convert it to a string. The following example replaces the String used in the previous example to concatenate 1000 random characters in the range to 0x0001 to 0x052F with a StringBuilder object.

using namespace System;
using namespace System::IO;
using namespace System::Text;

void main()
{
   Random^ rnd = gcnew Random();

   StringBuilder^ sb = gcnew StringBuilder();
   StreamWriter^ sw = gcnew StreamWriter(".\\StringFile.txt", 
                        false, Encoding::Unicode);

   for (int ctr = 0; ctr <= 1000; ctr++) {
      sb->Append(Convert::ToChar(rnd->Next(1, 0x0530))); 
      if (sb->Length % 60 == 0)
         sb->AppendLine();          
   }                    
   sw->Write(sb->ToString());
   sw->Close();
}

using System;
using System.IO;
using System.Text;

public class Example
{
   public static void Main()
   {
      Random rnd = new Random();
      StringBuilder sb = new StringBuilder();
      StreamWriter sw = new StreamWriter(@".\StringFile.txt", 
                                         false, Encoding.Unicode);

      for (int ctr = 0; ctr <= 1000; ctr++) {
         sb.Append((char)rnd.Next(1, 0x0530));
         if (sb.Length % 60 == 0)
            sb.AppendLine();          
      }                    
      sw.Write(sb.ToString());
      sw.Close();
   }
}

open System
open System.IO
open System.Text

do
    let rnd = Random()
    let sb = StringBuilder()
    use sw = new StreamWriter(@".\StringFile.txt", false, Encoding.Unicode)

    for _ = 0 to 1000 do
        sb.Append(rnd.Next(1, 0x0530) |> char) |> ignore
        if sb.Length % 60 = 0 then
            sb.AppendLine() |> ignore
    sw.Write(string sb)

Imports System.IO
Imports System.Text

Module Example
   Public Sub Main()
      Dim rnd As New Random()
      Dim sb As New StringBuilder()
      Dim sw As New StreamWriter(".\StringFile.txt", 
                                 False, Encoding.Unicode)

      For ctr As Integer = 0 To 1000
         sb.Append(ChrW(rnd.Next(1, &h0530))) 
         If sb.Length Mod 60 = 0 Then sb.AppendLine()          
      Next                    
      sw.Write(sb.ToString())
      sw.Close()
   End Sub
End Module

Ordinal vs. culture-sensitive operations

Members of the String class perform either ordinal or culture-sensitive (linguistic) operations on a String object. An ordinal operation acts on the numeric value of each Char object. A culture-sensitive operation acts on the value of the String object, and takes culture-specific casing, sorting, formatting, and parsing rules into account. Culture-sensitive operations execute in the context of an explicitly declared culture or the implicit current culture. The two kinds of operations can produce very different results when they are performed on the same string.

.NET also supports culture-insensitive linguistic string operations by using the invariant culture (CultureInfo.InvariantCulture), which is loosely based on the culture settings of the English language independent of region. Unlike other System.Globalization.CultureInfo settings, the settings of the invariant culture are guaranteed to remain consistent on a single computer, from system to system, and across versions of .NET. The invariant culture can be seen as a kind of black box that ensures stability of string comparisons and ordering across all cultures.

Important

If your application makes a security decision about a symbolic identifier such as a file name or named pipe, or about persisted data such as the text-based data in an XML file, the operation should use an ordinal comparison instead of a culture-sensitive comparison. This is because a culture-sensitive comparison can yield different results depending on the culture in effect, whereas an ordinal comparison depends solely on the binary value of the compared characters.

Important

Most methods that perform string operations include an overload that has a parameter of type StringComparison, which enables you to specify whether the method performs an ordinal or culture-sensitive operation. In general, you should call this overload to make the intent of your method call clear. For best practices and guidance for using ordinal and culture-sensitive operations on strings, see Best Practices for Using Strings.

Operations for casing, parsing and formatting, comparison and sorting, and testing for equality can be either ordinal or culture-sensitive. The following sections discuss each category of operation.

Tip

You should always call a method overload that makes the intent of your method call clear. For example, instead of calling the Compare(String, String) method to perform a culture-sensitive comparison of two strings by using the conventions of the current culture, you should call the Compare(String, String, StringComparison) method with a value of StringComparison.CurrentCulture for the comparisonType argument. For more information, see Best Practices for Using Strings.

You can download the sorting weight tables, a set of text files that contain information on the character weights used in sorting and comparison operations, from the following links:

Windows (.NET Framework and .NET Core): Sorting Weight Tables
Windows 10 May 2019 Update or later (.NET 5+) and Linux and macOS (.NET Core and .NET 5+): Default Unicode Collation Element Table

Casing

Casing rules determine how to change the capitalization of a Unicode character; for example, from lowercase to uppercase. Often, a casing operation is performed before a string comparison. For example, a string might be converted to uppercase so that it can be compared with another uppercase string. You can convert the characters in a string to lowercase by calling the ToLower or ToLowerInvariant method, and you can convert them to uppercase by calling the ToUpper or ToUpperInvariant method. In addition, you can use the TextInfo.ToTitleCase method to convert a string to title case.

Note

.NET Core running on Linux and macOS systems only: The collation behavior for the C and Posix cultures is always case-sensitive because these cultures do not use the expected Unicode collation order. We recommend that you use a culture other than C or Posix for performing culture-sensitive, case-insensitive sorting operations.

Casing operations can be based on the rules of the current culture, a specified culture, or the invariant culture. Because case mappings can vary depending on the culture used, the result of casing operations can vary based on culture. The actual differences in casing are of three kinds:

Differences in the case mapping of LATIN CAPITAL LETTER I (U+0049), LATIN SMALL LETTER I (U+0069), LATIN CAPITAL LETTER I WITH DOT ABOVE (U+0130), and LATIN SMALL LETTER DOTLESS I (U+0131). In the tr-TR (Turkish (Turkey)) and az-Latn-AZ (Azerbaijan, Latin) cultures, and in the tr, az, and az-Latn neutral cultures, the lowercase equivalent of LATIN CAPITAL LETTER I is LATIN SMALL LETTER DOTLESS I, and the uppercase equivalent of LATIN SMALL LETTER I is LATIN CAPITAL LETTER I WITH DOT ABOVE. In all other cultures, including the invariant culture, LATIN SMALL LETTER I and LATIN CAPITAL LETTER I are lowercase and uppercase equivalents.

The following example demonstrates how a string comparison designed to prevent file system access can fail if it relies on a culture-sensitive casing comparison. (The casing conventions of the invariant culture should have been used.)

using System;
using System.Globalization;
using System.Threading;

public class Example
{
   const string disallowed = "file";
   
   public static void Main()
   {
      IsAccessAllowed(@"FILE:\\\c:\users\user001\documents\FinancialInfo.txt");
   }

   private static void IsAccessAllowed(String resource)
   {
      CultureInfo[] cultures = { CultureInfo.CreateSpecificCulture("en-US"),
                                 CultureInfo.CreateSpecificCulture("tr-TR") };
      String scheme = null;
      int index = resource.IndexOfAny( new Char[] { '\\', '/' } );
      if (index > 0) 
         scheme = resource.Substring(0, index - 1);

      // Change the current culture and perform the comparison.
      foreach (var culture in cultures) {
         Thread.CurrentThread.CurrentCulture = culture;
         Console.WriteLine("Culture: {0}", CultureInfo.CurrentCulture.DisplayName);
         Console.WriteLine(resource);
         Console.WriteLine("Access allowed: {0}", 
                           ! String.Equals(disallowed, scheme, StringComparison.CurrentCultureIgnoreCase));      
         Console.WriteLine();
      }   
   }
}
// The example displays the following output:
//       Culture: English (United States)
//       FILE:\\\c:\users\user001\documents\FinancialInfo.txt
//       Access allowed: False
//       
//       Culture: Turkish (Turkey)
//       FILE:\\\c:\users\user001\documents\FinancialInfo.txt
//       Access allowed: True

open System
open System.Globalization
open System.Threading

let disallowed = "file"

let isAccessAllowed (resource: string) =
    let cultures = 
        [| CultureInfo.CreateSpecificCulture "en-US"
           CultureInfo.CreateSpecificCulture "tr-TR" |]
    let index = resource.IndexOfAny [| '\\'; '/' |]
    let scheme =
        if index > 0 then
            resource.Substring(0, index - 1)
        else 
            null

    // Change the current culture and perform the comparison.
    for culture in cultures do
        Thread.CurrentThread.CurrentCulture <- culture
        printfn $"Culture: {CultureInfo.CurrentCulture.DisplayName}"
        printfn $"{resource}"
        printfn $"Access allowed: {String.Equals(disallowed, scheme, StringComparison.CurrentCultureIgnoreCase) |> not}"
        printfn ""
        
isAccessAllowed @"FILE:\\\c:\users\user001\documents\FinancialInfo.txt"
// The example displays the following output:
//       Culture: English (United States)
//       FILE:\\\c:\users\user001\documents\FinancialInfo.txt
//       Access allowed: False
//
//       Culture: Turkish (Turkey)
//       FILE:\\\c:\users\user001\documents\FinancialInfo.txt
//       Access allowed: True

Imports System.Globalization
Imports System.Threading

Module Example
   Const disallowed = "file"
   
   Public Sub Main()
      IsAccessAllowed("FILE:\\\c:\users\user001\documents\FinancialInfo.txt")
   End Sub

   Private Sub IsAccessAllowed(resource As String)
      Dim cultures() As CultureInfo = { CultureInfo.CreateSpecificCulture("en-US"),
                                        CultureInfo.CreateSpecificCulture("tr-TR") }
      Dim scheme As String = Nothing
      Dim index As Integer = resource.IndexOfAny( {"\"c, "/"c })
      If index > 0 Then scheme = resource.Substring(0, index - 1)

      ' Change the current culture and perform the comparison.
      For Each culture In cultures
         Thread.CurrentThread.CurrentCulture = culture
         Console.WriteLine("Culture: {0}", CultureInfo.CurrentCulture.DisplayName)
         Console.WriteLine(resource)
         Console.WriteLine("Access allowed: {0}", 
                           Not String.Equals(disallowed, scheme, StringComparison.CurrentCultureIgnoreCase))      
         Console.WriteLine()
      Next   
   End Sub      
End Module
' The example displays the following output:
'       Culture: English (United States)
'       FILE:\\\c:\users\user001\documents\FinancialInfo.txt
'       Access allowed: False
'       
'       Culture: Turkish (Turkey)
'       FILE:\\\c:\users\user001\documents\FinancialInfo.txt
'       Access allowed: True

Differences in case mappings between the invariant culture and all other cultures. In these cases, using the casing rules of the invariant culture to change a character to uppercase or lowercase returns the same character. For all other cultures, it returns a different character. Some of the affected characters are listed in the following table.

Character	If changed to	Returns
MICRON SIGN (U+00B5)	Uppercase	GREEK CAPITAL LETTER MU (U+-39C)
LATIN CAPITAL LETTER I WITH DOT ABOVE (U+0130)	Lowercase	LATIN SMALL LETTER I (U+0069)
LATIN SMALL LETTER DOTLESS I (U+0131)	Uppercase	LATIN CAPITAL LETTER I (U+0049)
LATIN SMALL LETTER LONG S (U+017F)	Uppercase	LATIN CAPITAL LETTER S (U+0053)
LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON (U+01C5)	Lowercase	LATIN SMALL LETTER DZ WITH CARON (U+01C6)
COMBINING GREEK YPOGEGRAMMENI (U+0345)	Uppercase	GREEK CAPITAL LETTER IOTA (U+0399)

Differences in case mappings of two-letter mixed-case pairs in the ASCII character range. In most cultures, a two-letter mixed-case pair is equal to the equivalent two-letter uppercase or lowercase pair. This is not true for the following two-letter pairs in the following cultures, because in each case they are compared to a digraph:
- "lJ" and "nJ" in the hr-HR (Croatian (Croatia)) culture.
- "cH" in the cs-CZ (Czech (Czech Republic)) and sk-SK (Slovak (Slovakia)) cultures.
- "aA" in the da-DK (Danish (Denmark)) culture.
- "cS", "dZ", "dZS", "nY", "sZ", "tY", and "zS" in the hu-HU (Hungarian (Hungary)) culture.
- "cH" and "lL" in the es-ES_tradnl (Spanish (Spain, Traditional Sort)) culture.
- "cH", "gI", "kH", "nG" "nH", "pH", "qU', "tH", and "tR" in the vi-VN (Vietnamese (Vietnam)) culture.
However, it is unusual to encounter a situation in which a culture-sensitive comparison of these pairs creates problems, because these pairs are uncommon in fixed strings or identifiers.

The following example illustrates some of the differences in casing rules between cultures when converting strings to uppercase.

using namespace System;
using namespace System::Globalization;
using namespace System::IO;

String^ ShowHexValue(String^ s);

void main()
{
   StreamWriter^ sw = gcnew StreamWriter(".\\case.txt");   
   array<String^>^ words = gcnew array<String^> { L"file", L"sıfır", L"ǅenana" };
   array<CultureInfo^>^ cultures = gcnew array<CultureInfo^> { CultureInfo::InvariantCulture, 
                                                               gcnew CultureInfo("en-US"),  
                                                               gcnew CultureInfo("tr-TR") };

   for each (String^ word in words) {
      sw->WriteLine("{0}:", word);
      for each (CultureInfo^ culture in cultures) {
         String^ name = String::IsNullOrEmpty(culture->Name) ? 
                              "Invariant" : culture->Name;
         String^ upperWord = word->ToUpper(culture);
         sw->WriteLine("   {0,10}: {1,7} {2, 38}", name, 
                        upperWord, ShowHexValue(upperWord));

      }
      sw->WriteLine();  
   }
   sw->Close();
}

String^ ShowHexValue(String^ s)
{
   String^ retval = nullptr;
   for each (Char ch in s) {
      array<Byte>^ bytes = BitConverter::GetBytes(ch);
      retval += String::Format("{0:X2} {1:X2} ", bytes[1], bytes[0]);     
   }
   return retval;
} 
// The example displays the following output: 
//    file: 
//        Invariant:    FILE               00 46 00 49 00 4C 00 45  
//            en-US:    FILE               00 46 00 49 00 4C 00 45  
//            tr-TR:    FİLE               00 46 01 30 00 4C 00 45  
//     
//    sıfır: 
//        Invariant:   SıFıR         00 53 01 31 00 46 01 31 00 52  
//            en-US:   SIFIR         00 53 00 49 00 46 00 49 00 52  
//            tr-TR:   SIFIR         00 53 00 49 00 46 00 49 00 52  
//     
//    ǅenana: 
//        Invariant:  ǅENANA   01 C5 00 45 00 4E 00 41 00 4E 00 41  
//            en-US:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41  
//            tr-TR:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41

using System;
using System.Globalization;
using System.IO;

public class Example
{
   public static void Main()
   {
      StreamWriter sw = new StreamWriter(@".\case.txt");   
      string[] words = { "file", "sıfır", "ǅenana" };
      CultureInfo[] cultures = { CultureInfo.InvariantCulture, 
                                 new CultureInfo("en-US"),  
                                 new CultureInfo("tr-TR") };

      foreach (var word in words) {
         sw.WriteLine("{0}:", word);
         foreach (var culture in cultures) {
            string name = String.IsNullOrEmpty(culture.Name) ? 
                                 "Invariant" : culture.Name;
            string upperWord = word.ToUpper(culture);
            sw.WriteLine("   {0,10}: {1,7} {2, 38}", name, 
                         upperWord, ShowHexValue(upperWord));
         }
         sw.WriteLine();  
      }
      sw.Close();
   }

   private static string ShowHexValue(string s)
   {
      string retval = null;
      foreach (var ch in s) {
         byte[] bytes = BitConverter.GetBytes(ch);
         retval += String.Format("{0:X2} {1:X2} ", bytes[1], bytes[0]);     
      }
      return retval;
   } 
}
// The example displays the following output:
//    file:
//        Invariant:    FILE               00 46 00 49 00 4C 00 45 
//            en-US:    FILE               00 46 00 49 00 4C 00 45 
//            tr-TR:    FİLE               00 46 01 30 00 4C 00 45 
//    
//    sıfır:
//        Invariant:   SıFıR         00 53 01 31 00 46 01 31 00 52 
//            en-US:   SIFIR         00 53 00 49 00 46 00 49 00 52 
//            tr-TR:   SIFIR         00 53 00 49 00 46 00 49 00 52 
//    
//    ǅenana:
//        Invariant:  ǅENANA   01 C5 00 45 00 4E 00 41 00 4E 00 41 
//            en-US:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41 
//            tr-TR:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41

open System
open System.Globalization
open System.IO

let showHexValue (s: string) =
    let mutable retval = ""
    for ch in s do
        let bytes = BitConverter.GetBytes ch
        retval <- retval + String.Format("{0:X2} {1:X2} ", bytes[1], bytes[0])
    retval

do
    use sw = new StreamWriter(@".\case.txt")
    let words = [| "file"; "sıfır"; "ǅenana" |]
    let cultures = 
        [| CultureInfo.InvariantCulture 
           CultureInfo "en-US"
           CultureInfo "tr-TR" |]

    for word in words do
        sw.WriteLine("{0}:", word)
        for culture in cultures do
            let name =
                 if String.IsNullOrEmpty culture.Name then "Invariant" else culture.Name
            let upperWord = word.ToUpper culture
            sw.WriteLine("   {0,10}: {1,7} {2, 38}", name, upperWord, showHexValue upperWord)
        sw.WriteLine()
    sw.Close()

// The example displays the following output:
//    file:
//        Invariant:    FILE               00 46 00 49 00 4C 00 45
//            en-US:    FILE               00 46 00 49 00 4C 00 45
//            tr-TR:    FİLE               00 46 01 30 00 4C 00 45
//
//    sıfır:
//        Invariant:   SıFıR         00 53 01 31 00 46 01 31 00 52
//            en-US:   SIFIR         00 53 00 49 00 46 00 49 00 52
//            tr-TR:   SIFIR         00 53 00 49 00 46 00 49 00 52
//
//    ǅenana:
//        Invariant:  ǅENANA   01 C5 00 45 00 4E 00 41 00 4E 00 41
//            en-US:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41
//            tr-TR:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41

Imports System.Globalization
Imports System.IO

Module Example
   Public Sub Main()
      Dim sw As New StreamWriter(".\case.txt")   
      Dim words As String() = { "file", "sıfır", "ǅenana" }
      Dim cultures() As CultureInfo = { CultureInfo.InvariantCulture, 
                                        New CultureInfo("en-US"),  
                                        New CultureInfo("tr-TR") }

      For Each word In words
         sw.WriteLine("{0}:", word)
         For Each culture In cultures
            Dim name As String = If(String.IsNullOrEmpty(culture.Name),  
                                 "Invariant", culture.Name)
            Dim upperWord As String = word.ToUpper(culture)
            sw.WriteLine("   {0,10}: {1,7} {2, 38}", name, 
                         upperWord, ShowHexValue(upperWord))
     
         Next
         sw.WriteLine()  
      Next
      sw.Close()
   End Sub

   Private Function ShowHexValue(s As String) As String
      Dim retval As String = Nothing
      For Each ch In s
         Dim bytes() As Byte = BitConverter.GetBytes(ch)
         retval += String.Format("{0:X2} {1:X2} ", bytes(1), bytes(0))     
      Next
      Return retval
   End Function
End Module
' The example displays the following output:
'    file:
'        Invariant:    FILE               00 46 00 49 00 4C 00 45 
'            en-US:    FILE               00 46 00 49 00 4C 00 45 
'            tr-TR:    FİLE               00 46 01 30 00 4C 00 45 
'    
'    sıfır:
'        Invariant:   SıFıR         00 53 01 31 00 46 01 31 00 52 
'            en-US:   SIFIR         00 53 00 49 00 46 00 49 00 52 
'            tr-TR:   SIFIR         00 53 00 49 00 46 00 49 00 52 
'    
'    ǅenana:
'        Invariant:  ǅENANA   01 C5 00 45 00 4E 00 41 00 4E 00 41 
'            en-US:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41 
'            tr-TR:  ǄENANA   01 C4 00 45 00 4E 00 41 00 4E 00 41

Parsing and formatting

Formatting and parsing are inverse operations. Formatting rules determine how to convert a value, such as a date and time or a number, to its string representation, whereas parsing rules determine how to convert a string representation to a value such as a date and time. Both formatting and parsing rules are dependent on cultural conventions. The following example illustrates the ambiguity that can arise when interpreting a culture-specific date string. Without knowing the conventions of the culture that was used to produce a date string, it is not possible to know whether 03/01/2011, 3/1/2011, and 01/03/2011 represent January 3, 2011 or March 1, 2011.

using namespace System;
using namespace System::Globalization;

void main()
{
   DateTime^ date = gcnew DateTime(2011, 3, 1);
   array<CultureInfo^>^ cultures = gcnew array<CultureInfo^> { CultureInfo::InvariantCulture, 
                                                               gcnew CultureInfo("en-US"), 
                                                               gcnew CultureInfo("fr-FR") };

   for each (CultureInfo^ culture in cultures)
      Console::WriteLine("{0,-12} {1}", String::IsNullOrEmpty(culture->Name) ?
                        "Invariant" : culture->Name, 
                        date->ToString("d", culture));                                    
}
// The example displays the following output: 
//       Invariant    03/01/2011 
//       en-US        3/1/2011 
//       fr-FR        01/03/2011

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      DateTime date = new DateTime(2011, 3, 1);
      CultureInfo[] cultures = { CultureInfo.InvariantCulture, 
                                 new CultureInfo("en-US"), 
                                 new CultureInfo("fr-FR") };

      foreach (var culture in cultures)
         Console.WriteLine("{0,-12} {1}", String.IsNullOrEmpty(culture.Name) ?
                           "Invariant" : culture.Name, 
                           date.ToString("d", culture));                                    
   }
}
// The example displays the following output:
//       Invariant    03/01/2011
//       en-US        3/1/2011
//       fr-FR        01/03/2011

open System
open System.Globalization

let date = DateTime(2011, 3, 1)
let cultures = 
      [| CultureInfo.InvariantCulture
         CultureInfo "en-US"
         CultureInfo "fr-FR" |]

for culture in cultures do
    printfn $"""{(if String.IsNullOrEmpty culture.Name then "Invariant" else culture.Name),-12} {date.ToString("d", culture)}"""
// The example displays the following output:
//       Invariant    03/01/2011
//       en-US        3/1/2011
//       fr-FR        01/03/2011

Imports System.Globalization

Module Example
   Public Sub Main()
      Dim dat As Date = #3/1/2011#
      Dim cultures() As CultureInfo = { CultureInfo.InvariantCulture, 
                                        New CultureInfo("en-US"), 
                                        New CultureInfo("fr-FR") }

      For Each culture In cultures
         Console.WriteLine("{0,-12} {1}", If(String.IsNullOrEmpty(culture.Name), 
                           "Invariant", culture.Name), 
                           dat.ToString("d", culture))
      Next                                                         
   End Sub
End Module
' The example displays the following output:
'       Invariant    03/01/2011
'       en-US        3/1/2011
'       fr-FR        01/03/2011

Similarly, as the following example shows, a single string can produce different dates depending on the culture whose conventions are used in the parsing operation.

using namespace System;
using namespace System::Globalization;

void main()
{
   String^ dateString = "07/10/2011";
   array<CultureInfo^>^ cultures = gcnew array<CultureInfo^> { CultureInfo::InvariantCulture, 
                                                               CultureInfo::CreateSpecificCulture("en-GB"), 
                                                               CultureInfo::CreateSpecificCulture("en-US") };
   Console::WriteLine("{0,-12} {1,10} {2,8} {3,8}\n", "Date String", "Culture", 
                                                "Month", "Day");
   for each (CultureInfo^ culture in cultures) {
      DateTime date = DateTime::Parse(dateString, culture);
      Console::WriteLine("{0,-12} {1,10} {2,8} {3,8}", dateString, 
                        String::IsNullOrEmpty(culture->Name) ?
                        "Invariant" : culture->Name, 
                        date.Month, date.Day);
   }                      
}
// The example displays the following output: 
//       Date String     Culture    Month      Day 
//        
//       07/10/2011    Invariant        7       10 
//       07/10/2011        en-GB       10        7 
//       07/10/2011        en-US        7       10

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      string dateString = "07/10/2011";
      CultureInfo[] cultures = { CultureInfo.InvariantCulture, 
                                 CultureInfo.CreateSpecificCulture("en-GB"), 
                                 CultureInfo.CreateSpecificCulture("en-US") };
      Console.WriteLine("{0,-12} {1,10} {2,8} {3,8}\n", "Date String", "Culture", 
                                                 "Month", "Day");
      foreach (var culture in cultures) {
         DateTime date = DateTime.Parse(dateString, culture);
         Console.WriteLine("{0,-12} {1,10} {2,8} {3,8}", dateString, 
                           String.IsNullOrEmpty(culture.Name) ?
                           "Invariant" : culture.Name, 
                           date.Month, date.Day);
      }                      
   }
}
// The example displays the following output:
//       Date String     Culture    Month      Day
//       
//       07/10/2011    Invariant        7       10
//       07/10/2011        en-GB       10        7
//       07/10/2011        en-US        7       10

open System
open System.Globalization

let dateString = "07/10/2011"
let cultures = 
    [| CultureInfo.InvariantCulture
       CultureInfo.CreateSpecificCulture "en-GB"
       CultureInfo.CreateSpecificCulture "en-US" |]
printfn $"""{"Date String",-12} {"Culture",10} {"Month",8} {"Day",8}\n"""
for culture in cultures do
    let date = DateTime.Parse(dateString, culture)
    printfn $"""{dateString,-12} {(if String.IsNullOrEmpty culture.Name then "Invariant" else culture.Name),10} {date.Month,8} {date.Day,8}"""
// The example displays the following output:
//       Date String     Culture    Month      Day
//
//       07/10/2011    Invariant        7       10
//       07/10/2011        en-GB       10        7
//       07/10/2011        en-US        7       10

Imports System.Globalization

Module Example
   Public Sub Main()
      Dim dateString As String = "07/10/2011"
      Dim cultures() As CultureInfo = { CultureInfo.InvariantCulture, 
                                        CultureInfo.CreateSpecificCulture("en-GB"), 
                                        CultureInfo.CreateSpecificCulture("en-US") }
      Console.WriteLine("{0,-12} {1,10} {2,8} {3,8}", "Date String", "Culture", 
                                                 "Month", "Day")
      Console.WriteLine()                                                 
      For Each culture In cultures
         Dim dat As Date = DateTime.Parse(dateString, culture)
         Console.WriteLine("{0,-12} {1,10} {2,8} {3,8}", dateString, 
                           If(String.IsNullOrEmpty(culture.Name), 
                           "Invariant", culture.Name), 
                           dat.Month, dat.Day)
      Next
   End Sub
End Module
' The example displays the following output:
'       Date String     Culture    Month      Day
'       
'       07/10/2011    Invariant        7       10
'       07/10/2011        en-GB       10        7
'       07/10/2011        en-US        7       10

String comparison and sorting

Conventions for comparing and sorting strings vary from culture to culture. For example, the sort order may be based on phonetics or on the visual representation of characters. In East Asian languages, characters are sorted by the stroke and radical of ideographs. Sorting also depends on the order languages and cultures use for the alphabet. For example, the Danish language has an "Æ" character that it sorts after "Z" in the alphabet. In addition, comparisons can be case-sensitive or case-insensitive, and casing rules might differ by culture. Ordinal comparison, on the other hand, uses the Unicode code points of individual characters in a string when comparing and sorting strings.

Sort rules determine the alphabetic order of Unicode characters and how two strings compare to each other. For example, the String.Compare(String, String, StringComparison) method compares two strings based on the StringComparison parameter. If the parameter value is StringComparison.CurrentCulture, the method performs a linguistic comparison that uses the conventions of the current culture; if the parameter value is StringComparison.Ordinal, the method performs an ordinal comparison. Consequently, as the following example shows, if the current culture is U.S. English, the first call to the String.Compare(String, String, StringComparison) method (using culture-sensitive comparison) considers "a" less than "A", but the second call to the same method (using ordinal comparison) considers "a" greater than "A".

using namespace System;
using namespace System::Globalization;
using namespace System::Threading;

void main()
{
   Thread::CurrentThread->CurrentCulture = CultureInfo::CreateSpecificCulture("en-US");
   Console::WriteLine(String::Compare("A", "a", StringComparison::CurrentCulture));
   Console::WriteLine(String::Compare("A", "a", StringComparison::Ordinal));
}
// The example displays the following output: 
//       1 
//       -32

using System;
using System.Globalization;
using System.Threading;

public class Example
{
   public static void Main()
   {
      Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-US");
      Console.WriteLine(String.Compare("A", "a", StringComparison.CurrentCulture));
      Console.WriteLine(String.Compare("A", "a", StringComparison.Ordinal));
   }
}
// The example displays the following output:
//       1
//       -32

open System
open System.Globalization
open System.Threading

Thread.CurrentThread.CurrentCulture <- CultureInfo.CreateSpecificCulture "en-US"
printfn $"""{String.Compare("A", "a", StringComparison.CurrentCulture)}"""
printfn $"""{String.Compare("A", "a", StringComparison.Ordinal)}"""
// The example displays the following output:
//       1
//       -32

Imports System.Globalization
Imports System.Threading

Module Example
   Public Sub Main()
      Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("en-US")
      Console.WriteLine(String.Compare("A", "a", StringComparison.CurrentCulture))
      Console.WriteLine(String.Compare("A", "a", StringComparison.Ordinal))
   End Sub
End Module
' The example displays the following output:
'       1                                                                                     
'       -32

.NET supports word, string, and ordinal sort rules:

A word sort performs a culture-sensitive comparison of strings in which certain nonalphanumeric Unicode characters might have special weights assigned to them. For example, the hyphen (-) might have a very small weight assigned to it so that "coop" and "co-op" appear next to each other in a sorted list. For a list of the String methods that compare two strings using word sort rules, see the String operations by category section.
A string sort also performs a culture-sensitive comparison. It is similar to a word sort, except that there are no special cases, and all nonalphanumeric symbols come before all alphanumeric Unicode characters. Two strings can be compared using string sort rules by calling the CompareInfo.Compare method overloads that have an options parameter that is supplied a value of CompareOptions.StringSort. Note that this is the only method that .NET provides to compare two strings using string sort rules.
An ordinal sort compares strings based on the numeric value of each Char object in the string. An ordinal comparison is automatically case-sensitive because the lowercase and uppercase versions of a character have different code points. However, if case is not important, you can specify an ordinal comparison that ignores case. This is equivalent to converting the string to uppercase by using the invariant culture and then performing an ordinal comparison on the result. For a list of the String methods that compare two strings using ordinal sort rules, see the String operations by category section.

A culture-sensitive comparison is any comparison that explicitly or implicitly uses a CultureInfo object, including the invariant culture that is specified by the CultureInfo.InvariantCulture property. The implicit culture is the current culture, which is specified by the Thread.CurrentCulture and CultureInfo.CurrentCulture properties. There is considerable variation in the sort order of alphabetic characters (that is, characters for which the Char.IsLetter property returns true) across cultures. You can specify a culture-sensitive comparison that uses the conventions of a specific culture by supplying a CultureInfo object to a string comparison method such as Compare(String, String, CultureInfo, CompareOptions). You can specify a culture-sensitive comparison that uses the conventions of the current culture by supplying StringComparison.CurrentCulture, StringComparison.CurrentCultureIgnoreCase, or any member of the CompareOptions enumeration other than CompareOptions.Ordinal or CompareOptions.OrdinalIgnoreCase to an appropriate overload of the Compare method. A culture-sensitive comparison is generally appropriate for sorting whereas an ordinal comparison is not. An ordinal comparison is generally appropriate for determining whether two strings are equal (that is, for determining identity) whereas a culture-sensitive comparison is not.

The following example illustrates the difference between culture-sensitive and ordinal comparison. The example evaluates three strings, "Apple", "Æble", and "AEble", using ordinal comparison and the conventions of the da-DK and en-US cultures (each of which is the default culture at the time the Compare method is called). Because the Danish language treats the character "Æ" as an individual letter and sorts it after "Z" in the alphabet, the string "Æble" is greater than "Apple". However, "Æble" is not considered equivalent to "AEble", so "Æble" is also greater than "AEble". The en-US culture doesn't include the letter"Æ" but treats it as equivalent to "AE", which explains why "Æble" is less than "Apple" but equal to "AEble". Ordinal comparison, on the other hand, considers "Apple" to be less than "Æble", and "Æble" to be greater than "AEble".

using System;
using System.Globalization;
using System.Threading;

public class CompareStringSample
{
   public static void Main()
   {
      string str1 = "Apple";
      string str2 = "Æble"; 
      string str3 = "AEble";
      
      // Set the current culture to Danish in Denmark.
      Thread.CurrentThread.CurrentCulture = new CultureInfo("da-DK");
      Console.WriteLine("Current culture: {0}", 
                        CultureInfo.CurrentCulture.Name);
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str1, str2, String.Compare(str1, str2));
      Console.WriteLine("Comparison of {0} with {1}: {2}\n", 
                        str2, str3, String.Compare(str2, str3));
      
      // Set the current culture to English in the U.S.
      Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
      Console.WriteLine("Current culture: {0}", 
                        CultureInfo.CurrentCulture.Name);
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str1, str2, String.Compare(str1, str2));
      Console.WriteLine("Comparison of {0} with {1}: {2}\n", 
                        str2, str3, String.Compare(str2, str3));
      
      // Perform an ordinal comparison.
      Console.WriteLine("Ordinal comparison");
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str1, str2, 
                        String.Compare(str1, str2, StringComparison.Ordinal));
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str2, str3, 
                        String.Compare(str2, str3, StringComparison.Ordinal));
   }
}
// The example displays the following output:
//       Current culture: da-DK
//       Comparison of Apple with Æble: -1
//       Comparison of Æble with AEble: 1
//       
//       Current culture: en-US
//       Comparison of Apple with Æble: 1
//       Comparison of Æble with AEble: 0
//       
//       Ordinal comparison
//       Comparison of Apple with Æble: -133
//       Comparison of Æble with AEble: 133

open System
open System.Globalization
open System.Threading

let str1 = "Apple"
let str2 = "Æble"
let str3 = "AEble"

// Set the current culture to Danish in Denmark.
Thread.CurrentThread.CurrentCulture <- CultureInfo "da-DK"
printfn $"Current culture: {CultureInfo.CurrentCulture.Name}"
printfn $"Comparison of {str1} with {str2}: {String.Compare(str1, str2)}"
printfn $"Comparison of {str2} with {str3}: {String.Compare(str2, str3)}\n"

// Set the current culture to English in the U.S.
Thread.CurrentThread.CurrentCulture <- CultureInfo "en-US"
printfn $"Current culture: {CultureInfo.CurrentCulture.Name}"
printfn $"Comparison of {str1} with {str2}: {String.Compare(str1, str2)}"
printfn $"Comparison of {str2} with {str3}: {String.Compare(str2, str3)}\n"

// Perform an ordinal comparison.
printfn "Ordinal comparison"
printfn $"Comparison of {str1} with {str2}: {String.Compare(str1, str2, StringComparison.Ordinal)}"
printfn $"Comparison of {str2} with {str3}: {String.Compare(str2, str3, StringComparison.Ordinal)}"
// The example displays the following output:
//       Current culture: da-DK
//       Comparison of Apple with Æble: -1
//       Comparison of Æble with AEble: 1
//
//       Current culture: en-US
//       Comparison of Apple with Æble: 1
//       Comparison of Æble with AEble: 0
//
//       Ordinal comparison
//       Comparison of Apple with Æble: -133
//       Comparison of Æble with AEble: 133

Imports System.Globalization
Imports System.Threading

Public Module Example
   Public Sub Main()
      Dim str1 As String = "Apple"
      Dim str2 As String = "Æble"
      Dim str3 As String = "AEble"
      
      ' Set the current culture to Danish in Denmark.
      Thread.CurrentThread.CurrentCulture = New CultureInfo("da-DK")
      Console.WriteLine("Current culture: {0}", 
                        CultureInfo.CurrentCulture.Name)
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str1, str2, String.Compare(str1, str2))
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str2, str3, String.Compare(str2, str3))
      Console.WriteLine()
      
      ' Set the current culture to English in the U.S.
      Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
      Console.WriteLine("Current culture: {0}", 
                        CultureInfo.CurrentCulture.Name)
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str1, str2, String.Compare(str1, str2))
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str2, str3, String.Compare(str2, str3))
      Console.WriteLine()
      
      ' Perform an ordinal comparison.
      Console.WriteLine("Ordinal comparison")
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str1, str2, 
                        String.Compare(str1, str2, StringComparison.Ordinal))
      Console.WriteLine("Comparison of {0} with {1}: {2}", 
                        str2, str3, 
                        String.Compare(str2, str3, StringComparison.Ordinal))
   End Sub
End Module
' The example displays the following output:
'       Current culture: da-DK
'       Comparison of Apple with Æble: -1
'       Comparison of Æble with AEble: 1
'       
'       Current culture: en-US
'       Comparison of Apple with Æble: 1
'       Comparison of Æble with AEble: 0
'       
'       Ordinal comparison
'       Comparison of Apple with Æble: -133
'       Comparison of Æble with AEble: 133

Use the following general guidelines to choose an appropriate sorting or string comparison method:

If you want the strings to be ordered based on the user's culture, you should order them based on the conventions of the current culture. If the user's culture changes, the order of sorted strings will also change accordingly. For example, a thesaurus application should always sort words based on the user's culture.
If you want the strings to be ordered based on the conventions of a specific culture, you should order them by supplying a CultureInfo object that represents that culture to a comparison method. For example, in an application designed to teach students a particular language, you want strings to be ordered based on the conventions of one of the cultures that speaks that language.
If you want the order of strings to remain unchanged across cultures, you should order them based on the conventions of the invariant culture or use an ordinal comparison. For example, you would use an ordinal sort to organize the names of files, processes, mutexes, or named pipes.
For a comparison that involves a security decision (such as whether a username is valid), you should always perform an ordinal test for equality by calling an overload of the Equals method.

Note

The culture-sensitive sorting and casing rules used in string comparison depend on the version of the .NET. On .NET Core, string comparison depends on the version of the Unicode Standard supported by the underlying operating system. In .NET Framework 4.5 and later versions running on Windows 8 or later, sorting, casing, normalization, and Unicode character information conform to the Unicode 6.0 standard. On other Windows operating systems, they conform to the Unicode 5.0 standard.

For more information about word, string, and ordinal sort rules, see the System.Globalization.CompareOptions topic. For additional recommendations on when to use each rule, see Best Practices for Using Strings.

Ordinarily, you don't call string comparison methods such as Compare directly to determine the sort order of strings. Instead, comparison methods are called by sorting methods such as Array.Sort or List<T>.Sort. The following example performs four different sorting operations (word sort using the current culture, word sort using the invariant culture, ordinal sort, and string sort using the invariant culture) without explicitly calling a string comparison method, although they do specify the type of comparison to use. Note that each type of sort produces a unique ordering of strings in its array.

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Generic;
using namespace System::Globalization;

// IComparer<String> implementation to perform string sort. 
ref class SCompare : System::Collections::Generic::IComparer<String^>
{
public:
   SCompare() {};

   virtual int Compare(String^ x, String^ y)
   {
      return CultureInfo::CurrentCulture->CompareInfo->Compare(x, y, CompareOptions::StringSort);
   }
};

void main()
{
   array<String^>^ strings = gcnew array<String^> { "coop", "co-op", "cooperative", 
                                                    L"co\x00ADoperative", L"c�ur", "coeur" };

   // Perform a word sort using the current (en-US) culture. 
   array<String^>^ current = gcnew array<String^>(strings->Length); 
   strings->CopyTo(current, 0); 
   Array::Sort(current, StringComparer::CurrentCulture);

   // Perform a word sort using the invariant culture. 
   array<String^>^ invariant = gcnew array<String^>(strings->Length);
   strings->CopyTo(invariant, 0); 
   Array::Sort(invariant, StringComparer::InvariantCulture);

   // Perform an ordinal sort. 
   array<String^>^ ordinal = gcnew array<String^>(strings->Length);
   strings->CopyTo(ordinal, 0); 
   Array::Sort(ordinal, StringComparer::Ordinal);

   // Perform a string sort using the current culture. 
   array<String^>^ stringSort = gcnew array<String^>(strings->Length);
   strings->CopyTo(stringSort, 0); 
   Array::Sort(stringSort, gcnew SCompare());

   // Display array values
   Console::WriteLine("{0,13} {1,13} {2,15} {3,13} {4,13}\n", 
                     "Original", "Word Sort", "Invariant Word", 
                     "Ordinal Sort", "String Sort");
   for (int ctr = 0; ctr < strings->Length; ctr++)
      Console::WriteLine("{0,13} {1,13} {2,15} {3,13} {4,13}", 
                         strings[ctr], current[ctr], invariant[ctr], 
                         ordinal[ctr], stringSort[ctr] );          
}
// The example displays the following output: 
//         Original     Word Sort  Invariant Word  Ordinal Sort   String Sort 
//     
//             coop          c�ur            c�ur         co-op         co-op 
//            co-op         coeur           coeur         coeur          c�ur 
//      cooperative          coop            coop          coop         coeur 
//      co�operative         co-op           co-op   cooperative          coop 
//             c�ur   cooperative     cooperative   co�operative   cooperative 
//            coeur   co�operative     co�operative          c�ur   co�operative

using System;
using System.Collections;
using System.Collections.Generic;
using System.Globalization;
 
public class Example
{
   public static void Main()
   {
      string[] strings = { "coop", "co-op", "cooperative", 
                           "co\u00ADoperative", "cœur", "coeur" };

      // Perform a word sort using the current (en-US) culture.
      string[] current = new string[strings.Length]; 
      strings.CopyTo(current, 0); 
      Array.Sort(current, StringComparer.CurrentCulture);

      // Perform a word sort using the invariant culture.
      string[] invariant = new string[strings.Length];
      strings.CopyTo(invariant, 0); 
      Array.Sort(invariant, StringComparer.InvariantCulture);

      // Perform an ordinal sort.
      string[] ordinal = new string[strings.Length];
      strings.CopyTo(ordinal, 0); 
      Array.Sort(ordinal, StringComparer.Ordinal);

      // Perform a string sort using the current culture.
      string[] stringSort = new string[strings.Length];
      strings.CopyTo(stringSort, 0); 
      Array.Sort(stringSort, new SCompare());

      // Display array values
      Console.WriteLine("{0,13} {1,13} {2,15} {3,13} {4,13}\n", 
                        "Original", "Word Sort", "Invariant Word", 
                        "Ordinal Sort", "String Sort");
      for (int ctr = 0; ctr < strings.Length; ctr++)
         Console.WriteLine("{0,13} {1,13} {2,15} {3,13} {4,13}", 
                           strings[ctr], current[ctr], invariant[ctr], 
                           ordinal[ctr], stringSort[ctr] );          
   }
}

// IComparer<String> implementation to perform string sort.
internal class SCompare : IComparer<String>
{
   public int Compare(string x, string y)
   {
      return CultureInfo.CurrentCulture.CompareInfo.Compare(x, y, CompareOptions.StringSort);
   }
}
// The example displays the following output:
//         Original     Word Sort  Invariant Word  Ordinal Sort   String Sort
//    
//             coop          cœur            cœur         co-op         co-op
//            co-op         coeur           coeur         coeur          cœur
//      cooperative          coop            coop          coop         coeur
//     cooperative         co-op           co-op   cooperative          coop
//             cœur   cooperative     cooperative  cooperative   cooperative
//            coeur  cooperative    cooperative          cœur  cooperative

open System
open System.Collections.Generic
open System.Globalization

// IComparer<String> implementation to perform string sort using an F# object expression.
let scompare = 
    { new IComparer<String> with
        member _.Compare(x, y) =
            CultureInfo.CurrentCulture.CompareInfo.Compare(x, y, CompareOptions.StringSort) }

let strings = [| "coop"; "co-op"; "cooperative"; "co\u00ADoperative"; "cœur"; "coeur" |]

// Perform a word sort using the current (en-US) culture.
let current = Array.copy strings
Array.Sort(current, StringComparer.CurrentCulture)

// Perform a word sort using the invariant culture.
let invariant = Array.copy strings
Array.Sort(invariant, StringComparer.InvariantCulture)

// Perform an ordinal sort.
let ordinal = Array.copy strings
Array.Sort(ordinal, StringComparer.Ordinal)

// Perform a string sort using the current culture.
let stringSort = Array.copy strings
Array.Sort(stringSort, scompare)

// Display array values
printfn "%13s %13s %15s %13s %13s\n" "Original" "Word Sort" "Invariant Word" "Ordinal Sort" "String Sort"
for i = 0 to strings.Length - 1 do
    printfn "%13s %13s %15s %13s %13s\n" strings[i] current[i] invariant[i] ordinal[i] stringSort[i]

// The example displays the following output:
//         Original     Word Sort  Invariant Word  Ordinal Sort   String Sort
//
//             coop          cœur            cœur         co-op         co-op
//            co-op         coeur           coeur         coeur          cœur
//      cooperative          coop            coop          coop         coeur
//     cooperative         co-op           co-op   cooperative          coop
//             cœur   cooperative     cooperative  cooperative   cooperative
//            coeur  cooperative    cooperative          cœur  cooperative

Imports System.Collections
Imports System.Collections.Generic
Imports System.Globalization

Module Example
   Public Sub Main()
      Dim strings() As String = { "coop", "co-op", "cooperative", 
                                  "co" + ChrW(&h00AD) + "operative", 
                                  "cœur", "coeur" }

      ' Perform a word sort using the current (en-US) culture.
      Dim current(strings.Length - 1) As String  
      strings.CopyTo(current, 0) 
      Array.Sort(current, StringComparer.CurrentCulture)

      ' Perform a word sort using the invariant culture.
      Dim invariant(strings.Length - 1) As String
      strings.CopyTo(invariant, 0) 
      Array.Sort(invariant, StringComparer.InvariantCulture)

      ' Perform an ordinal sort.
      Dim ordinal(strings.Length - 1) As String
      strings.CopyTo(ordinal, 0) 
      Array.Sort(ordinal, StringComparer.Ordinal)

      ' Perform a string sort using the current culture.
      Dim stringSort(strings.Length - 1) As String
      strings.CopyTo(stringSort, 0) 
      Array.Sort(stringSort, new SCompare())

      ' Display array values
      Console.WriteLine("{0,13} {1,13} {2,15} {3,13} {4,13}", 
                        "Original", "Word Sort", "Invariant Word", 
                        "Ordinal Sort", "String Sort")
      Console.WriteLine()
                                                      
      For ctr As Integer = 0 To strings.Length - 1
         Console.WriteLine("{0,13} {1,13} {2,15} {3,13} {4,13}", 
                           strings(ctr), current(ctr), invariant(ctr), 
                           ordinal(ctr), stringSort(ctr))   
      Next                                  
   End Sub
End Module

' IComparer<String> implementation to perform string sort.
Friend Class SCompare : Implements IComparer(Of String)
   Public Function Compare(x As String, y As String) As Integer _
                   Implements IComparer(Of String).Compare
      Return CultureInfo.CurrentCulture.CompareInfo.Compare(x, y, CompareOptions.StringSort)
   End Function
End Class
' The example displays the following output:
'         Original     Word Sort  Invariant Word  Ordinal Sort   String Sort
'    
'             coop          cœur            cœur         co-op         co-op
'            co-op         coeur           coeur         coeur          cœur
'      cooperative          coop            coop          coop         coeur
'     cooperative         co-op           co-op   cooperative          coop
'             cœur   cooperative     cooperative  cooperative   cooperative
'            coeur  cooperative    cooperative          cœur  cooperative

Tip

Internally, .NET uses sort keys to support culturally sensitive string comparison. Each character in a string is given several categories of sort weights, including alphabetic, case, and diacritic. A sort key, represented by the SortKey class, provides a repository of these weights for a particular string. If your app performs a large number of searching or sorting operations on the same set of strings, you can improve its performance by generating and storing sort keys for all the strings that it uses. When a sort or comparison operation is required, you use the sort keys instead of the strings. For more information, see the SortKey class.

If you don't specify a string comparison convention, sorting methods such as Array.Sort(Array) perform a culture-sensitive, case-sensitive sort on strings. The following example illustrates how changing the current culture affects the order of sorted strings in an array. It creates an array of three strings. First, it sets the System.Threading.Thread.CurrentThread.CurrentCulture property to en-US and calls the Array.Sort(Array) method. The resulting sort order is based on sorting conventions for the English (United States) culture. Next, the example sets the System.Threading.Thread.CurrentThread.CurrentCulture property to da-DK and calls the Array.Sort method again. Notice how the resulting sort order differs from the en-US results because it uses the sorting conventions for Danish (Denmark).

using System;
using System.Globalization;
using System.Threading;

public class ArraySort
{
   public static void Main(String[] args)
   {
      // Create and initialize a new array to store the strings.
      string[] stringArray = { "Apple", "Æble", "Zebra"};

      // Display the values of the array.
      Console.WriteLine( "The original string array:");
      PrintIndexAndValues(stringArray);

      // Set the CurrentCulture to "en-US".
      Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
      // Sort the values of the array.
      Array.Sort(stringArray);

      // Display the values of the array.
      Console.WriteLine("After sorting for the culture \"en-US\":");
      PrintIndexAndValues(stringArray);

      // Set the CurrentCulture to "da-DK".
      Thread.CurrentThread.CurrentCulture = new CultureInfo("da-DK");
      // Sort the values of the Array.
      Array.Sort(stringArray);

      // Display the values of the array.
      Console.WriteLine("After sorting for the culture \"da-DK\":");
      PrintIndexAndValues(stringArray);
   }
   public static void PrintIndexAndValues(string[] myArray)
   {
      for (int i = myArray.GetLowerBound(0); i <=
            myArray.GetUpperBound(0); i++ )
         Console.WriteLine("[{0}]: {1}", i, myArray[i]);
      Console.WriteLine();
   }
}
// The example displays the following output:
//       The original string array:
//       [0]: Apple
//       [1]: Æble
//       [2]: Zebra
//
//       After sorting for the "en-US" culture:
//       [0]: Æble
//       [1]: Apple
//       [2]: Zebra
//
//       After sorting for the culture "da-DK":
//       [0]: Apple
//       [1]: Zebra
//       [2]: Æble

open System
open System.Globalization
open System.Threading

let printIndexAndValues (myArray: string[]) =
    for i = myArray.GetLowerBound 0 to myArray.GetUpperBound 0 do
        printfn $"[{i}]: {myArray[i]}" 
    printfn ""

// Create and initialize a new array to store the strings.
let stringArray = [| "Apple"; "Æble"; "Zebra" |]

// Display the values of the array.
printfn "The original string array:"
printIndexAndValues stringArray

// Set the CurrentCulture to "en-US".
Thread.CurrentThread.CurrentCulture <- CultureInfo "en-US"
// Sort the values of the array.
Array.Sort stringArray

// Display the values of the array.
printfn "After sorting for the culture \"en-US\":"
printIndexAndValues stringArray

// Set the CurrentCulture to "da-DK".
Thread.CurrentThread.CurrentCulture <- CultureInfo "da-DK"
// Sort the values of the Array.
Array.Sort stringArray

// Display the values of the array.
printfn "After sorting for the culture \"da-DK\":"
printIndexAndValues stringArray
// The example displays the following output:
//       The original string array:
//       [0]: Apple
//       [1]: Æble
//       [2]: Zebra
//
//       After sorting for the "en-US" culture:
//       [0]: Æble
//       [1]: Apple
//       [2]: Zebra
//
//       After sorting for the culture "da-DK":
//       [0]: Apple
//       [1]: Zebra
//       [2]: Æble

Imports System.Globalization
Imports System.IO
Imports System.Threading

Public Class TextToFile   
   Public Shared Sub Main()
      ' Creates and initializes a new array to store 
      ' these date/time objects.
      Dim stringArray() As String = { "Apple", "Æble", "Zebra"}
      
      ' Displays the values of the array.
      Console.WriteLine("The original string array:")
      PrintIndexAndValues(stringArray)
      
      ' Set the CurrentCulture to "en-US".
      Thread.CurrentThread.CurrentCulture = New CultureInfo("en-US")
      ' Sort the values of the Array.
      Array.Sort(stringArray)
      
      ' Display the values of the array.
      Console.WriteLine("After sorting for the ""en-US"" culture:")
      PrintIndexAndValues(stringArray)
      
      ' Set the CurrentCulture to "da-DK".
      Thread.CurrentThread.CurrentCulture = New CultureInfo("da-DK")
      ' Sort the values of the Array.
      Array.Sort(stringArray)
      
      ' Displays the values of the Array.
      Console.WriteLine("After sorting for the culture ""da-DK"":")
      PrintIndexAndValues(stringArray)
   End Sub

   Public Shared Sub PrintIndexAndValues(myArray() As String)
      For i As Integer = myArray.GetLowerBound(0) To myArray.GetUpperBound(0)
         Console.WriteLine("[{0}]: {1}", i, myArray(i))
      Next
      Console.WriteLine()
   End Sub 
End Class
' The example displays the following output:
'       The original string array:
'       [0]: Apple
'       [1]: Æble
'       [2]: Zebra
'       
'       After sorting for the "en-US" culture:
'       [0]: Æble
'       [1]: Apple
'       [2]: Zebra
'       
'       After sorting for the culture "da-DK":
'       [0]: Apple
'       [1]: Zebra
'       [2]: Æble

Warning

If your primary purpose in comparing strings is to determine whether they are equal, you should call the String.Equals method. Typically, you should use Equals to perform an ordinal comparison. The String.Compare method is intended primarily to sort strings.

String search methods, such as String.StartsWith and String.IndexOf, also can perform culture-sensitive or ordinal string comparisons. The following example illustrates the differences between ordinal and culture-sensitive comparisons using the IndexOf method. A culture-sensitive search in which the current culture is English (United States) considers the substring "oe" to match the ligature "œ". Because a soft hyphen (U+00AD) is a zero-width character, the search treats the soft hyphen as equivalent to Empty and finds a match at the beginning of the string. An ordinal search, on the other hand, does not find a match in either case.

using namespace System;

void FindInString(String^ s, String^ substring, StringComparison options);

void main()
{
   // Search for "oe" and "�u" in "�ufs" and "oeufs".
   String^ s1 = L"�ufs";
   String^ s2 = L"oeufs";
   FindInString(s1, "oe", StringComparison::CurrentCulture);
   FindInString(s1, "oe", StringComparison::Ordinal);
   FindInString(s2, "�u", StringComparison::CurrentCulture);
   FindInString(s2, "�u", StringComparison::Ordinal);
   Console::WriteLine();

   String^ s3 = L"co\x00ADoperative";
   FindInString(s3, L"\x00AD", StringComparison::CurrentCulture);
   FindInString(s3, L"\x00AD", StringComparison::Ordinal);
}

void FindInString(String^ s, String^ substring, StringComparison options)
{
   int result = s->IndexOf(substring, options);
   if (result != -1)
      Console::WriteLine("'{0}' found in {1} at position {2}", 
                        substring, s, result);
   else
      Console::WriteLine("'{0}' not found in {1}", 
                        substring, s);                                                  
}
// The example displays the following output:
//      'oe' found in oufs at position 0
//      'oe' not found in oufs
//      'ou' found in oeufs at position 0
//      'ou' not found in oeufs
//
//      '-' found in co-operative at position 0
//      '-' found in co-operative at position 2

using System;

public class Example
{
   public static void Main()
   {
      // Search for "oe" and "œu" in "œufs" and "oeufs".
      string s1 = "œufs";
      string s2 = "oeufs";
      FindInString(s1, "oe", StringComparison.CurrentCulture);
      FindInString(s1, "oe", StringComparison.Ordinal);
      FindInString(s2, "œu", StringComparison.CurrentCulture);
      FindInString(s2, "œu", StringComparison.Ordinal);
      Console.WriteLine();
      
      string s3 = "co\u00ADoperative";
      FindInString(s3, "\u00AD", StringComparison.CurrentCulture);
      FindInString(s3, "\u00AD", StringComparison.Ordinal);
   }

   private static void FindInString(string s, string substring, StringComparison options)
   {
      int result = s.IndexOf(substring, options);
      if (result != -1)
         Console.WriteLine("'{0}' found in {1} at position {2}", 
                           substring, s, result);
      else
         Console.WriteLine("'{0}' not found in {1}", 
                           substring, s);                                                  
   }
}
// The example displays the following output:
//       'oe' found in œufs at position 0
//       'oe' not found in œufs
//       'œu' found in oeufs at position 0
//       'œu' not found in oeufs
//       
//       '' found in cooperative at position 0
//       '' found in cooperative at position 2

open System

let findInString (s: string) (substring: string) (options: StringComparison) =
    let result = s.IndexOf(substring, options)
    if result <> -1 then
        printfn $"'{substring}' found in {s} at position {result}"
    else
        printfn $"'{substring}' not found in {s}"

// Search for "oe" and "œu" in "œufs" and "oeufs".
let s1 = "œufs"
let s2 = "oeufs"
findInString s1 "oe" StringComparison.CurrentCulture
findInString s1 "oe" StringComparison.Ordinal
findInString s2 "œu" StringComparison.CurrentCulture
findInString s2 "œu" StringComparison.Ordinal
printfn ""

let s3 = "co\u00ADoperative"
findInString s3 "\u00AD" StringComparison.CurrentCulture
findInString s3 "\u00AD" StringComparison.Ordinal

// The example displays the following output:
//       'oe' found in œufs at position 0
//       'oe' not found in œufs
//       'œu' found in oeufs at position 0
//       'œu' not found in oeufs
//
//       '' found in cooperative at position 0
//       '' found in cooperative at position 2

Module Example
   Public Sub Main()
      ' Search for "oe" and "œu" in "œufs" and "oeufs".
      Dim s1 As String = "œufs"
      Dim s2 As String = "oeufs"
      FindInString(s1, "oe", StringComparison.CurrentCulture)
      FindInString(s1, "oe", StringComparison.Ordinal)
      FindInString(s2, "œu", StringComparison.CurrentCulture)
      FindInString(s2, "œu", StringComparison.Ordinal)
      Console.WriteLine()
      
      Dim softHyphen As String = ChrW(&h00AD)
      Dim s3 As String = "co" + softHyphen + "operative"
      FindInString(s3, softHyphen, StringComparison.CurrentCulture)
      FindInString(s3, softHyphen, StringComparison.Ordinal)
   End Sub

   Private Sub FindInString(s As String, substring As String, 
                            options As StringComparison)
      Dim result As Integer = s.IndexOf(substring, options)
      If result <> -1
         Console.WriteLine("'{0}' found in {1} at position {2}", 
                           substring, s, result)
      Else
         Console.WriteLine("'{0}' not found in {1}", 
                           substring, s)
      End If                                                                          
   End Sub
End Module
' The example displays the following output:
'       'oe' found in œufs at position 0
'       'oe' not found in œufs
'       'œu' found in oeufs at position 0
'       'œu' not found in oeufs
'       
'       '' found in cooperative at position 0
'       '' found in cooperative at position 2

Search in strings

String search methods, such as String.StartsWith and String.IndexOf, also can perform culture-sensitive or ordinal string comparisons to determine whether a character or substring is found in a specified string.

The search methods in the String class that search for an individual character, such as the IndexOf method, or one of a set of characters, such as the IndexOfAny method, all perform an ordinal search. To perform a culture-sensitive search for a character, you must call a CompareInfo method such as CompareInfo.IndexOf(String, Char) or CompareInfo.LastIndexOf(String, Char). Note that the results of searching for a character using ordinal and culture-sensitive comparison can be very different. For example, a search for a precomposed Unicode character such as the ligature "Æ" (U+00C6) might match any occurrence of its components in the correct sequence, such as "AE" (U+041U+0045), depending on the culture. The following example illustrates the difference between the String.IndexOf(Char) and CompareInfo.IndexOf(String, Char) methods when searching for an individual character. The ligature "æ" (U+00E6) is found in the string "aerial" when using the conventions of the en-US culture, but not when using the conventions of the da-DK culture or when performing an ordinal comparison.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      String[] cultureNames = { "da-DK", "en-US" };
      CompareInfo ci;
      String str = "aerial";
      Char ch = 'æ';  // U+00E6
      
      Console.Write("Ordinal comparison -- ");
      Console.WriteLine("Position of '{0}' in {1}: {2}", ch, str,
                        str.IndexOf(ch));
      
      foreach (var cultureName in cultureNames) {
         ci = CultureInfo.CreateSpecificCulture(cultureName).CompareInfo;
         Console.Write("{0} cultural comparison -- ", cultureName);
         Console.WriteLine("Position of '{0}' in {1}: {2}", ch, str,
                           ci.IndexOf(str, ch));
      }
   }
}
// The example displays the following output:
//       Ordinal comparison -- Position of 'æ' in aerial: -1
//       da-DK cultural comparison -- Position of 'æ' in aerial: -1
//       en-US cultural comparison -- Position of 'æ' in aerial: 0

open System.Globalization

let cultureNames = [| "da-DK"; "en-US" |]
let str = "aerial"
let ch = 'æ'  // U+00E6

printf "Ordinal comparison -- "
printfn $"Position of '{ch}' in {str}: {str.IndexOf ch}"
                  
for cultureName in cultureNames do
    let ci = CultureInfo.CreateSpecificCulture(cultureName).CompareInfo
    printf $"{cultureName} cultural comparison -- "
    printfn $"Position of '{ch}' in {str}: {ci.IndexOf(str, ch)}"
// The example displays the following output:
//       Ordinal comparison -- Position of 'æ' in aerial: -1
//       da-DK cultural comparison -- Position of 'æ' in aerial: -1
//       en-US cultural comparison -- Position of 'æ' in aerial: 0

Imports System.Globalization

Module Example
   Public Sub Main()
      Dim cultureNames() As String = { "da-DK", "en-US" }
      Dim ci As CompareInfo
      Dim str As String = "aerial"
      Dim ch As Char = "æ"c  ' U+00E6
      
      Console.Write("Ordinal comparison -- ")
      Console.WriteLine("Position of '{0}' in {1}: {2}", ch, str,
                        str.IndexOf(ch))
      
      For Each cultureName In cultureNames
         ci = CultureInfo.CreateSpecificCulture(cultureName).CompareInfo
         Console.Write("{0} cultural comparison -- ", cultureName)
         Console.WriteLine("Position of '{0}' in {1}: {2}", ch, str,
                           ci.IndexOf(str, ch))
      Next
   End Sub
End Module
' The example displays the following output:
'       Ordinal comparison -- Position of 'æ' in aerial: -1
'       da-DK cultural comparison -- Position of 'æ' in aerial: -1
'       en-US cultural comparison -- Position of 'æ' in aerial: 0

On the other hand, String class methods that search for a string rather than a character perform a culture-sensitive search if search options are not explicitly specified by a parameter of type StringComparison. The sole exception is Contains, which performs an ordinal search.

Testing for equality

Use the String.Compare method to determine the relationship of two strings in the sort order. Typically, this is a culture-sensitive operation. In contrast, call the String.Equals method to test for equality. Because the test for equality usually compares user input with some known string, such as a valid user name, a password, or a file system path, it is typically an ordinal operation.

Warning

It is possible to test for equality by calling the String.Compare method and determining whether the return value is zero. However, this practice is not recommended. To determine whether two strings are equal, you should call one of the overloads of the String.Equals method. The preferred overload to call is either the instance Equals(String, StringComparison) method or the static Equals(String, String, StringComparison) method, because both methods include a System.StringComparison parameter that explicitly specifies the type of comparison.

The following example illustrates the danger of performing a culture-sensitive comparison for equality when an ordinal one should be used instead. In this case, the intent of the code is to prohibit file system access from URLs that begin with "FILE://" or "file://" by performing a case-insensitive comparison of the beginning of a URL with the string "FILE://". However, if a culture-sensitive comparison is performed using the Turkish (Turkey) culture on a URL that begins with "file://", the comparison for equality fails, because the Turkish uppercase equivalent of the lowercase "i" is "İ" instead of "I". As a result, file system access is inadvertently permitted. On the other hand, if an ordinal comparison is performed, the comparison for equality succeeds, and file system access is denied.

using namespace System;
using namespace System::Globalization;
using namespace System::Threading;

bool TestForEquality(String^ str, StringComparison cmp);

void main()
{
   Thread::CurrentThread->CurrentCulture = CultureInfo::CreateSpecificCulture("tr-TR");      

   String^ filePath = "file://c:/notes.txt";

   Console::WriteLine("Culture-sensitive test for equality:");
   if (! TestForEquality(filePath, StringComparison::CurrentCultureIgnoreCase))
      Console::WriteLine("Access to {0} is allowed.", filePath);
   else
      Console::WriteLine("Access to {0} is not allowed.", filePath);

   Console::WriteLine("\nOrdinal test for equality:");
   if (! TestForEquality(filePath, StringComparison::OrdinalIgnoreCase))
      Console::WriteLine("Access to {0} is allowed.", filePath);
   else
      Console::WriteLine("Access to {0} is not allowed.", filePath);
}

bool TestForEquality(String^ str, StringComparison cmp)
{
      int position = str->IndexOf("://");
      if (position < 0) return false;

      String^ substring = str->Substring(0, position);  
      return substring->Equals("FILE", cmp);
}
// The example displays the following output: 
//       Culture-sensitive test for equality: 
//       Access to file://c:/notes.txt is allowed. 
//        
//       Ordinal test for equality: 
//       Access to file://c:/notes.txt is not allowed.

using System;
using System.Globalization;
using System.Threading;

public class Example
{
   public static void Main()
   {
      Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("tr-TR");      

      string filePath = "file://c:/notes.txt";
      
      Console.WriteLine("Culture-sensitive test for equality:");
      if (! TestForEquality(filePath, StringComparison.CurrentCultureIgnoreCase))
         Console.WriteLine("Access to {0} is allowed.", filePath);
      else
         Console.WriteLine("Access to {0} is not allowed.", filePath);
      
      Console.WriteLine("\nOrdinal test for equality:");
      if (! TestForEquality(filePath, StringComparison.OrdinalIgnoreCase))
         Console.WriteLine("Access to {0} is allowed.", filePath);
      else
         Console.WriteLine("Access to {0} is not allowed.", filePath);
   }

   private static bool TestForEquality(string str, StringComparison cmp)
   {
      int position = str.IndexOf("://");
      if (position < 0) return false;

      string substring = str.Substring(0, position);  
      return substring.Equals("FILE", cmp);
   }
}
// The example displays the following output:
//       Culture-sensitive test for equality:
//       Access to file://c:/notes.txt is allowed.
//       
//       Ordinal test for equality:
//       Access to file://c:/notes.txt is not allowed.

open System
open System.Globalization
open System.Threading

let testForEquality (str: string) (cmp: StringComparison) =
    let position = str.IndexOf "://"
    if position < 0 then false
    else
        let substring = str.Substring(0, position)
        substring.Equals("FILE", cmp)

Thread.CurrentThread.CurrentCulture <- CultureInfo.CreateSpecificCulture "tr-TR"

let filePath = "file://c:/notes.txt"

printfn "Culture-sensitive test for equality:"
if not (testForEquality filePath StringComparison.CurrentCultureIgnoreCase) then
    printfn $"Access to {filePath} is allowed."
else
    printfn $"Access to {filePath} is not allowed."

printfn "\nOrdinal test for equality:"
if not (testForEquality filePath StringComparison.OrdinalIgnoreCase) then
    printfn $"Access to {filePath} is allowed."
else
    printfn $"Access to {filePath} is not allowed."

// The example displays the following output:
//       Culture-sensitive test for equality:
//       Access to file://c:/notes.txt is allowed.
//
//       Ordinal test for equality:
//       Access to file://c:/notes.txt is not allowed.

Imports System.Globalization
Imports System.Threading

Module Example
   Public Sub Main()
      Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture("tr-TR")      

      Dim filePath As String = "file://c:/notes.txt"
      
      Console.WriteLine("Culture-sensitive test for equality:")
      If Not TestForEquality(filePath, StringComparison.CurrentCultureIgnoreCase) Then
         Console.WriteLine("Access to {0} is allowed.", filePath)
      Else
         Console.WriteLine("Access to {0} is not allowed.", filePath)
      End If       
      Console.WriteLine()
      
      Console.WriteLine("Ordinal test for equality:")
      If Not TestForEquality(filePath, StringComparison.OrdinalIgnoreCase) Then
         Console.WriteLine("Access to {0} is allowed.", filePath)
      Else
         Console.WriteLine("Access to {0} is not allowed.", filePath)
      End If       
   End Sub
   
   Private Function TestForEquality(str As String, cmp As StringComparison) As Boolean
      Dim position As Integer = str.IndexOf("://")
      If position < 0 Then Return False

      Dim substring As String = str.Substring(0, position)  
      Return substring.Equals("FILE", cmp)
   End Function
End Module
' The example displays the following output:
'       Culture-sensitive test for equality:
'       Access to file://c:/notes.txt is allowed.
'       
'       Ordinal test for equality:
'       Access to file://c:/notes.txt is not allowed.

Normalization

Some Unicode characters have multiple representations. For example, any of the following code points can represent the letter "ắ":

U+1EAF
U+0103 U+0301
U+0061 U+0306 U+0301

Multiple representations for a single character complicate searching, sorting, matching, and other string operations.

The Unicode standard defines a process called normalization that returns one binary representation of a Unicode character for any of its equivalent binary representations. Normalization can use several algorithms, called normalization forms, that follow different rules. .NET supports Unicode normalization forms C, D, KC, and KD. When strings have been normalized to the same normalization form, they can be compared by using ordinal comparison.

An ordinal comparison is a binary comparison of the Unicode scalar value of corresponding Char objects in each string. The String class includes a number of methods that can perform an ordinal comparison, including the following:

Any overload of the Compare, Equals, StartsWith, EndsWith, IndexOf, and LastIndexOf methods that includes a StringComparison parameter. The method performs an ordinal comparison if you supply a value of StringComparison.Ordinal or OrdinalIgnoreCase for this parameter.
The overloads of the CompareOrdinal method.
Methods that use ordinal comparison by default, such as Contains, Replace, and Split.
Methods that search for a Char value or for the elements in a Char array in a string instance. Such methods include IndexOf(Char) and Split(Char[]).

You can determine whether a string is normalized to normalization form C by calling the String.IsNormalized() method, or you can call the String.IsNormalized(NormalizationForm) method to determine whether a string is normalized to a specified normalization form. You can also call the String.Normalize() method to convert a string to normalization form C, or you can call the String.Normalize(NormalizationForm) method to convert a string to a specified normalization form. For step-by-step information about normalizing and comparing strings, see the Normalize() and Normalize(NormalizationForm) methods.

The following simple example illustrates string normalization. It defines the letter "ố" in three different ways in three different strings, and uses an ordinal comparison for equality to determine that each string differs from the other two strings. It then converts each string to the supported normalization forms, and again performs an ordinal comparison of each string in a specified normalization form. In each case, the second test for equality shows that the strings are equal.

using namespace System;
using namespace System::Globalization;
using namespace System::IO;
using namespace System::Text;

public ref class Example
{
private:
   StreamWriter^ sw;

   void TestForEquality(... array<String^>^  words)
   {
      for (int ctr = 0; ctr <= words->Length - 2; ctr++)
         for (int ctr2 = ctr + 1; ctr2 <= words->Length - 1; ctr2++) 
            sw->WriteLine("{0} ({1}) = {2} ({3}): {4}", 
                         words[ctr], ShowBytes(words[ctr]),
                         words[ctr2], ShowBytes(words[ctr2]),
                         words[ctr]->Equals(words[ctr2], StringComparison::Ordinal));
   }

   String^ ShowBytes(String^ str)
   {
      String^ result = nullptr;
      for each (Char ch in str)
         result += String::Format("{0} ", Convert::ToUInt16(ch).ToString("X4")); 
      return result->Trim();            
   } 

   array<String^>^ NormalizeStrings(NormalizationForm nf, ... array<String^>^ words)
   {
      for (int ctr = 0; ctr < words->Length; ctr++)
         if (! words[ctr]->IsNormalized(nf))
            words[ctr] = words[ctr]->Normalize(nf); 
      return words;   
   }

public: 
   void Execute()
   {
      sw = gcnew StreamWriter(".\\TestNorm1.txt");

      // Define three versions of the same word.  
      String^ s1 = L"sống";        // create word with U+1ED1 
      String^ s2 = L"s\x00F4\x0301ng";
      String^ s3 = L"so\x0302\x0301ng";

      TestForEquality(s1, s2, s3);      
      sw->WriteLine();

      // Normalize and compare strings using each normalization form. 
      for each (String^ formName in Enum::GetNames(NormalizationForm::typeid))
      {
         sw->WriteLine("Normalization {0}:\n", formName); 
         NormalizationForm nf = (NormalizationForm) Enum::Parse(NormalizationForm::typeid, formName);
         array<String^>^ sn = NormalizeStrings(nf, s1, s2, s3 );
         TestForEquality(sn);           
         sw->WriteLine("\n");                                        
      }

      sw->Close(); 
   }
};

void main()
{
   Example^ ex = gcnew Example();
   ex->Execute();
}
// The example produces the following output:
// The example displays the following output: 
//       sống (0073 1ED1 006E 0067) = sống (0073 00F4 0301 006E 0067): False 
//       sống (0073 1ED1 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False 
//       sống (0073 00F4 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False 
//        
//       Normalization FormC: 
//        
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True 
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True 
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True 
//        
//        
//       Normalization FormD: 
//        
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True 
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True 
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True 
//        
//        
//       Normalization FormKC: 
//        
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True 
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True 
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True 
//        
//        
//       Normalization FormKD: 
//        
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True 
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True 
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True

using System;
using System.Globalization;
using System.IO;
using System.Text;

public class Example
{
   private static StreamWriter sw;
   
   public static void Main()
   {
      sw = new StreamWriter(@".\TestNorm1.txt");

      // Define three versions of the same word. 
      string s1 = "sống";        // create word with U+1ED1
      string s2 = "s\u00F4\u0301ng";
      string s3 = "so\u0302\u0301ng";

      TestForEquality(s1, s2, s3);      
      sw.WriteLine();

      // Normalize and compare strings using each normalization form.
      foreach (string formName in Enum.GetNames(typeof(NormalizationForm)))
      {
         sw.WriteLine("Normalization {0}:\n", formName); 
         NormalizationForm nf = (NormalizationForm) Enum.Parse(typeof(NormalizationForm), formName);
         string[] sn = NormalizeStrings(nf, s1, s2, s3);
         TestForEquality(sn);           
         sw.WriteLine("\n");                                        
      }
      
      sw.Close();   
   }

   private static void TestForEquality(params string[] words)
   {
      for (int ctr = 0; ctr <= words.Length - 2; ctr++)
         for (int ctr2 = ctr + 1; ctr2 <= words.Length - 1; ctr2++) 
            sw.WriteLine("{0} ({1}) = {2} ({3}): {4}", 
                         words[ctr], ShowBytes(words[ctr]),
                         words[ctr2], ShowBytes(words[ctr2]),
                         words[ctr].Equals(words[ctr2], StringComparison.Ordinal));
   }

   private static string ShowBytes(string str)
   {
      string result = null;
      foreach (var ch in str)
         result += $"{(ushort)ch:X4} ";
      return result.Trim();            
   } 
   
   private static string[] NormalizeStrings(NormalizationForm nf, params string[] words)
   {
      for (int ctr = 0; ctr < words.Length; ctr++)
         if (! words[ctr].IsNormalized(nf))
            words[ctr] = words[ctr].Normalize(nf); 
      return words;   
   }
}
// The example displays the following output:
//       sống (0073 1ED1 006E 0067) = sống (0073 00F4 0301 006E 0067): False
//       sống (0073 1ED1 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False
//       sống (0073 00F4 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False
//       
//       Normalization FormC:
//       
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       
//       
//       Normalization FormD:
//       
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       
//       
//       Normalization FormKC:
//       
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       
//       
//       Normalization FormKD:
//       
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True

open System
open System.IO
open System.Text

do
    use sw = new StreamWriter(@".\TestNorm1.txt")

    let showBytes (str: string) =
        let mutable result = ""
        for ch in str do
            result <- result + $"{uint16 ch:X4} "
        result.Trim()
    
    let testForEquality (words: string[]) =
        for ctr = 0 to words.Length - 2 do
            for ctr2 = ctr + 1 to words.Length - 1 do
                sw.WriteLine("{0} ({1}) = {2} ({3}): {4}",
                            words[ctr], showBytes(words[ctr]),
                            words[ctr2], showBytes(words[ctr2]),
                            words[ctr].Equals(words[ctr2], StringComparison.Ordinal))

    let normalizeStrings nf (words: string[]) =
        for i = 0 to words.Length - 1 do
            if not (words[i].IsNormalized nf) then
                words[i] <- words[i].Normalize nf
        words

    // Define three versions of the same word.
    let s1 = "sống"        // create word with U+1ED1
    let s2 = "s\u00F4\u0301ng"
    let s3 = "so\u0302\u0301ng"

    testForEquality [| s1; s2; s3 |]
    sw.WriteLine()

    // Normalize and compare strings using each normalization form.
    for formName in Enum.GetNames typeof<NormalizationForm> do
        sw.WriteLine("Normalization {0}:\n", formName)
        let nf = Enum.Parse(typeof<NormalizationForm>, formName) :?> NormalizationForm
        let sn = normalizeStrings nf [| s1; s2; s3|]
        testForEquality sn
        sw.WriteLine "\n"

// The example displays the following output:
//       sống (0073 1ED1 006E 0067) = sống (0073 00F4 0301 006E 0067): False
//       sống (0073 1ED1 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False
//       sống (0073 00F4 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False
//
//       Normalization FormC:
//
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//
//
//       Normalization FormD:
//
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//
//
//       Normalization FormKC:
//
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
//
//
//       Normalization FormKD:
//
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
//       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True

Imports System.Globalization
Imports System.IO
Imports System.Text

Module Example
   Private sw As StreamWriter
       
   Public Sub Main()
      sw = New StreamWriter(".\TestNorm1.txt")

      ' Define three versions of the same word. 
      Dim s1 As String = "sống"        ' create word with U+1ED1
      Dim s2 AS String = "s" + ChrW(&h00F4) + ChrW(&h0301) + "ng"
      Dim s3 As String = "so" + ChrW(&h0302) + ChrW(&h0301) + "ng"

      TestForEquality(s1, s2, s3)      
      sw.WriteLine()

      ' Normalize and compare strings using each normalization form.
      For Each formName In [Enum].GetNames(GetType(NormalizationForm))
         sw.WriteLine("Normalization {0}:", formName) 
         Dim nf As NormalizationForm = CType([Enum].Parse(GetType(NormalizationForm), formName),  
                                             NormalizationForm)
         Dim sn() As String = NormalizeStrings(nf, s1, s2, s3)
         TestForEquality(sn)           
         sw.WriteLine(vbCrLf)                                        
      Next
      
      sw.Close()   
   End Sub

   Private Sub TestForEquality(ParamArray words As String())
      For ctr As Integer = 0 To words.Length - 2
         For ctr2 As Integer = ctr + 1 To words.Length - 1 
            sw.WriteLine("{0} ({1}) = {2} ({3}): {4}", 
                         words(ctr), ShowBytes(words(ctr)),
                         words(ctr2), ShowBytes(words(ctr2)),
                         words(ctr).Equals(words(ctr2), StringComparison.Ordinal))
         Next                
      Next   
   End Sub

   Private Function ShowBytes(str As String) As String
      Dim result As String = Nothing
      For Each ch In str
         result += String.Format("{0} ", Convert.ToUInt16(ch).ToString("X4")) 
      Next
      Return result.Trim()            
   End Function  
   
   Private Function NormalizeStrings(nf As NormalizationForm, ParamArray words() As String) As String()
      For ctr As Integer = 0 To words.Length - 1
         If Not words(ctr).IsNormalized(nf) Then
            words(ctr) = words(ctr).Normalize(nf)
         End If    
      Next
      Return words   
   End Function
End Module
' The example displays the following output:
'       sống (0073 1ED1 006E 0067) = sống (0073 00F4 0301 006E 0067): False
'       sống (0073 1ED1 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False
'       sống (0073 00F4 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): False
'       
'       Normalization FormC:
'       
'       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
'       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
'       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
'       
'       
'       Normalization FormD:
'       
'       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
'       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
'       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
'       
'       
'       Normalization FormKC:
'       
'       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
'       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
'       sống (0073 1ED1 006E 0067) = sống (0073 1ED1 006E 0067): True
'       
'       
'       Normalization FormKD:
'       
'       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
'       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True
'       sống (0073 006F 0302 0301 006E 0067) = sống (0073 006F 0302 0301 006E 0067): True

For more information about normalization and normalization forms, see System.Text.NormalizationForm, as well as Unicode Standard Annex #15: Unicode Normalization Forms and the Normalization FAQ on the unicode.org website.

String operations by category

The String class provides members for comparing strings, testing strings for equality, finding characters or substrings in a string, modifying a string, extracting substrings from a string, combining strings, formatting values, copying a string, and normalizing a string.

Compare strings

You can compare strings to determine their relative position in the sort order by using the following String methods:

Compare returns an integer that indicates the relationship of one string to a second string in the sort order.
CompareOrdinal returns an integer that indicates the relationship of one string to a second string based on a comparison of their code points.
CompareTo returns an integer that indicates the relationship of the current string instance to a second string in the sort order. The CompareTo(String) method provides the IComparable and IComparable<T> implementations for the String class.

Test strings for equality

You call the Equals method to determine whether two strings are equal. The instance Equals(String, String, StringComparison) and the static Equals(String, StringComparison) overloads let you specify whether the comparison is culture-sensitive or ordinal, and whether case is considered or ignored. Most tests for equality are ordinal, and comparisons for equality that determine access to a system resource (such as a file system object) should always be ordinal.

Find characters in a string

The String class includes two kinds of search methods:

Methods that return a Boolean value to indicate whether a particular substring is present in a string instance. These include the Contains, EndsWith, and StartsWith methods.
Methods that indicate the starting position of a substring in a string instance. These include the IndexOf, IndexOfAny, LastIndexOf, and LastIndexOfAny methods.

Warning

If you want to search a string for a particular pattern rather than a specific substring, you should use regular expressions. For more information, see .NET Regular Expressions.

Modify a string

The String class includes the following methods that appear to modify the value of a string:

Insert inserts a string into the current String instance.
PadLeft inserts one or more occurrences of a specified character at the beginning of a string.
PadRight inserts one or more occurrences of a specified character at the end of a string.
Remove deletes a substring from the current String instance.
Replace replaces a substring with another substring in the current String instance.
ToLower and ToLowerInvariant convert all the characters in a string to lowercase.
ToUpper and ToUpperInvariant convert all the characters in a string to uppercase.
Trim removes all occurrences of a character from the beginning and end of a string.
TrimEnd removes all occurrences of a character from the end of a string.
TrimStart removes all occurrences of a character from the beginning of a string.

Important

All string modification methods return a new String object. They don't modify the value of the current instance.

Extract substrings from a string

The String.Split method separates a single string into multiple strings. Overloads of the method allow you to specify multiple delimiters, to limit the number of substrings that the method extracts, to trim white space from substrings, and to specify whether empty strings (which occur when delimiters are adjacent) are included among the returned strings.

Combine strings

The following String methods can be used for string concatenation:

Concat combines one or more substrings into a single string.
Join concatenates one or more substrings into a single element and adds a separator between each substring.

Format values

The String.Format method uses the composite formatting feature to replace one or more placeholders in a string with the string representation of some object or value. The Format method is often used to do the following:

To embed the string representation of a numeric value in a string.
To embed the string representation of a date and time value in a string.
To embed the string representation of an enumeration value in a string.
To embed the string representation of some object that supports the IFormattable interface in a string.
To right-justify or left-justify a substring in a field within a larger string.

For detailed information about formatting operations and examples, see the Format overload summary.

Copy a string

You can call the following String methods to make a copy of a string:

Clone returns a reference to an existing String object.
Copy creates a copy of an existing string.
CopyTo copies a portion of a string to a character array.

Normalize a string

In Unicode, a single character can have multiple code points. Normalization converts these equivalent characters into the same binary representation. The String.Normalize method performs the normalization, and the String.IsNormalized method determines whether a string is normalized.

For more information and an example, see the Normalization section earlier in this topic.

Constructors

String(Char*)	Initializes a new instance of the String class to the value indicated by a specified pointer to an array of Unicode characters.
String(Char*, Int32, Int32)	Initializes a new instance of the String class to the value indicated by a specified pointer to an array of Unicode characters, a starting character position within that array, and a length.
String(Char, Int32)	Initializes a new instance of the String class to the value indicated by a specified Unicode character repeated a specified number of times.
String(Char[])	Initializes a new instance of the String class to the Unicode characters indicated in the specified character array.
String(Char[], Int32, Int32)	Initializes a new instance of the String class to the value indicated by an array of Unicode characters, a starting character position within that array, and a length.
String(ReadOnlySpan<Char>)	Initializes a new instance of the String class to the Unicode characters indicated in the specified read-only span.
String(SByte*)	Initializes a new instance of the String class to the value indicated by a pointer to an array of 8-bit signed integers.
String(SByte*, Int32, Int32)	Initializes a new instance of the String class to the value indicated by a specified pointer to an array of 8-bit signed integers, a starting position within that array, and a length.
String(SByte*, Int32, Int32, Encoding)	Initializes a new instance of the String class to the value indicated by a specified pointer to an array of 8-bit signed integers, a starting position within that array, a length, and an Encoding object.

Fields

Empty

Represents the empty string. This field is read-only.

Properties

Chars[Int32]	Gets the Char object at a specified position in the current String object.
Length	Gets the number of characters in the current String object.

Methods

Clone()	Returns a reference to this instance of String.
Compare(String, Int32, String, Int32, Int32)	Compares substrings of two specified String objects and returns an integer that indicates their relative position in the sort order.
Compare(String, Int32, String, Int32, Int32, Boolean)	Compares substrings of two specified String objects, ignoring or honoring their case, and returns an integer that indicates their relative position in the sort order.
Compare(String, Int32, String, Int32, Int32, Boolean, CultureInfo)	Compares substrings of two specified String objects, ignoring or honoring their case and using culture-specific information to influence the comparison, and returns an integer that indicates their relative position in the sort order.
Compare(String, Int32, String, Int32, Int32, CultureInfo, CompareOptions)	Compares substrings of two specified String objects using the specified comparison options and culture-specific information to influence the comparison, and returns an integer that indicates the relationship of the two substrings to each other in the sort order.
Compare(String, Int32, String, Int32, Int32, StringComparison)	Compares substrings of two specified String objects using the specified rules, and returns an integer that indicates their relative position in the sort order.
Compare(String, String)	Compares two specified String objects and returns an integer that indicates their relative position in the sort order.
Compare(String, String, Boolean)	Compares two specified String objects, ignoring or honoring their case, and returns an integer that indicates their relative position in the sort order.
Compare(String, String, Boolean, CultureInfo)	Compares two specified String objects, ignoring or honoring their case, and using culture-specific information to influence the comparison, and returns an integer that indicates their relative position in the sort order.
Compare(String, String, CultureInfo, CompareOptions)	Compares two specified String objects using the specified comparison options and culture-specific information to influence the comparison, and returns an integer that indicates the relationship of the two strings to each other in the sort order.
Compare(String, String, StringComparison)	Compares two specified String objects using the specified rules, and returns an integer that indicates their relative position in the sort order.
CompareOrdinal(String, Int32, String, Int32, Int32)	Compares substrings of two specified String objects by evaluating the numeric values of the corresponding Char objects in each substring.
CompareOrdinal(String, String)	Compares two specified String objects by evaluating the numeric values of the corresponding Char objects in each string.
CompareTo(Object)	Compares this instance with a specified Object and indicates whether this instance precedes, follows, or appears in the same position in the sort order as the specified Object.
CompareTo(String)	Compares this instance with a specified String object and indicates whether this instance precedes, follows, or appears in the same position in the sort order as the specified string.
Concat(IEnumerable<String>)	Concatenates the members of a constructed IEnumerable<T> collection of type String.
Concat(Object)	Creates the string representation of a specified object.
Concat(Object, Object)	Concatenates the string representations of two specified objects.
Concat(Object, Object, Object)	Concatenates the string representations of three specified objects.
Concat(Object, Object, Object, Object)	Concatenates the string representations of four specified objects and any objects specified in an optional variable length parameter list.
Concat(Object[])	Concatenates the string representations of the elements in a specified Object array.
Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>)	Concatenates the string representations of two specified read-only character spans.
Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>)	Concatenates the string representations of three specified read-only character spans.
Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>)	Concatenates the string representations of four specified read-only character spans.
Concat(String, String)	Concatenates two specified instances of String.
Concat(String, String, String)	Concatenates three specified instances of String.
Concat(String, String, String, String)	Concatenates four specified instances of String.
Concat(String[])	Concatenates the elements of a specified String array.
Concat<T>(IEnumerable<T>)	Concatenates the members of an IEnumerable<T> implementation.
Contains(Char)	Returns a value indicating whether a specified character occurs within this string.
Contains(Char, StringComparison)	Returns a value indicating whether a specified character occurs within this string, using the specified comparison rules.
Contains(String)	Returns a value indicating whether a specified substring occurs within this string.
Contains(String, StringComparison)	Returns a value indicating whether a specified string occurs within this string, using the specified comparison rules.
Copy(String)	Obsolete. Creates a new instance of String with the same value as a specified String.
CopyTo(Int32, Char[], Int32, Int32)	Copies a specified number of characters from a specified position in this instance to a specified position in an array of Unicode characters.
CopyTo(Span<Char>)	Copies the contents of this string into the destination span.
Create(IFormatProvider, DefaultInterpolatedStringHandler)	Creates a new string by using the specified provider to control the formatting of the specified interpolated string.
Create(IFormatProvider, Span<Char>, DefaultInterpolatedStringHandler)	Creates a new string by using the specified provider to control the formatting of the specified interpolated string.
Create<TState>(Int32, TState, SpanAction<Char,TState>)	Creates a new string with a specific length and initializes it after creation by using the specified callback.
EndsWith(Char)	Determines whether the end of this string instance matches the specified character.
EndsWith(String)	Determines whether the end of this string instance matches the specified string.
EndsWith(String, Boolean, CultureInfo)	Determines whether the end of this string instance matches the specified string when compared using the specified culture.
EndsWith(String, StringComparison)	Determines whether the end of this string instance matches the specified string when compared using the specified comparison option.
EnumerateRunes()	Returns an enumeration of Rune from this string.
Equals(Object)	Determines whether this instance and a specified object, which must also be a String object, have the same value.
Equals(String)	Determines whether this instance and another specified String object have the same value.
Equals(String, String)	Determines whether two specified String objects have the same value.
Equals(String, String, StringComparison)	Determines whether two specified String objects have the same value. A parameter specifies the culture, case, and sort rules used in the comparison.
Equals(String, StringComparison)	Determines whether this string and a specified String object have the same value. A parameter specifies the culture, case, and sort rules used in the comparison.
Format(IFormatProvider, CompositeFormat, Object[])	Replaces the format item or items in a CompositeFormat with the string representation of the corresponding objects in the specified format.
Format(IFormatProvider, CompositeFormat, ReadOnlySpan<Object>)	Replaces the format item or items in a CompositeFormat with the string representation of the corresponding objects in the specified format.
Format(IFormatProvider, String, Object)	Replaces the format item or items in a specified string with the string representation of the corresponding object. A parameter supplies culture-specific formatting information.
Format(IFormatProvider, String, Object, Object)	Replaces the format items in a string with the string representation of two specified objects. A parameter supplies culture-specific formatting information.
Format(IFormatProvider, String, Object, Object, Object)	Replaces the format items in a string with the string representation of three specified objects. An parameter supplies culture-specific formatting information.
Format(IFormatProvider, String, Object[])	Replaces the format items in a string with the string representations of corresponding objects in a specified array. A parameter supplies culture-specific formatting information.
Format(String, Object)	Replaces one or more format items in a string with the string representation of a specified object.
Format(String, Object, Object)	Replaces the format items in a string with the string representation of two specified objects.
Format(String, Object, Object, Object)	Replaces the format items in a string with the string representation of three specified objects.
Format(String, Object[])	Replaces the format item in a specified string with the string representation of a corresponding object in a specified array.
Format<TArg0,TArg1,TArg2>(IFormatProvider, CompositeFormat, TArg0, TArg1, TArg2)	Replaces the format item or items in a CompositeFormat with the string representation of the corresponding objects in the specified format.
Format<TArg0,TArg1>(IFormatProvider, CompositeFormat, TArg0, TArg1)	Replaces the format item or items in a CompositeFormat with the string representation of the corresponding objects in the specified format.
Format<TArg0>(IFormatProvider, CompositeFormat, TArg0)	Replaces the format item or items in a CompositeFormat with the string representation of the corresponding objects in the specified format.
GetEnumerator()	Retrieves an object that can iterate through the individual characters in this string.
GetHashCode()	Returns the hash code for this string.
GetHashCode(ReadOnlySpan<Char>)	Returns the hash code for the provided read-only character span.
GetHashCode(ReadOnlySpan<Char>, StringComparison)	Returns the hash code for the provided read-only character span using the specified rules.
GetHashCode(StringComparison)	Returns the hash code for this string using the specified rules.
GetPinnableReference()	Returns a reference to the element of the string at index zero. This method is intended to support .NET compilers and is not intended to be called by user code.
GetType()	Gets the Type of the current instance. (Inherited from Object)
GetTypeCode()	Returns the TypeCode for the String class.
IndexOf(Char)	Reports the zero-based index of the first occurrence of the specified Unicode character in this string.
IndexOf(Char, Int32)	Reports the zero-based index of the first occurrence of the specified Unicode character in this string. The search starts at a specified character position.
IndexOf(Char, Int32, Int32)	Reports the zero-based index of the first occurrence of the specified character in this instance. The search starts at a specified character position and examines a specified number of character positions.
IndexOf(Char, StringComparison)	Reports the zero-based index of the first occurrence of the specified Unicode character in this string. A parameter specifies the type of search to use for the specified character.
IndexOf(String)	Reports the zero-based index of the first occurrence of the specified string in this instance.
IndexOf(String, Int32)	Reports the zero-based index of the first occurrence of the specified string in this instance. The search starts at a specified character position.
IndexOf(String, Int32, Int32)	Reports the zero-based index of the first occurrence of the specified string in this instance. The search starts at a specified character position and examines a specified number of character positions.
IndexOf(String, Int32, Int32, StringComparison)	Reports the zero-based index of the first occurrence of the specified string in the current String object. Parameters specify the starting search position in the current string, the number of characters in the current string to search, and the type of search to use for the specified string.
IndexOf(String, Int32, StringComparison)	Reports the zero-based index of the first occurrence of the specified string in the current String object. Parameters specify the starting search position in the current string and the type of search to use for the specified string.
IndexOf(String, StringComparison)	Reports the zero-based index of the first occurrence of the specified string in the current String object. A parameter specifies the type of search to use for the specified string.
IndexOfAny(Char[])	Reports the zero-based index of the first occurrence in this instance of any character in a specified array of Unicode characters.
IndexOfAny(Char[], Int32)	Reports the zero-based index of the first occurrence in this instance of any character in a specified array of Unicode characters. The search starts at a specified character position.
IndexOfAny(Char[], Int32, Int32)	Reports the zero-based index of the first occurrence in this instance of any character in a specified array of Unicode characters. The search starts at a specified character position and examines a specified number of character positions.
Insert(Int32, String)	Returns a new string in which a specified string is inserted at a specified index position in this instance.
Intern(String)	Retrieves the system's reference to the specified String.
IsInterned(String)	Retrieves a reference to a specified String.
IsNormalized()	Indicates whether this string is in Unicode normalization form C.
IsNormalized(NormalizationForm)	Indicates whether this string is in the specified Unicode normalization form.
IsNullOrEmpty(String)	Indicates whether the specified string is `null` or an empty string ("").
IsNullOrWhiteSpace(String)	Indicates whether a specified string is `null`, empty, or consists only of white-space characters.
Join(Char, Object[])	Concatenates the string representations of an array of objects, using the specified separator between each member.
Join(Char, String[])	Concatenates an array of strings, using the specified separator between each member.
Join(Char, String[], Int32, Int32)	Concatenates an array of strings, using the specified separator between each member, starting with the element in `value` located at the `startIndex` position, and concatenating up to `count` elements.
Join(String, IEnumerable<String>)	Concatenates the members of a constructed IEnumerable<T> collection of type String, using the specified separator between each member.
Join(String, Object[])	Concatenates the elements of an object array, using the specified separator between each element.
Join(String, String[])	Concatenates all the elements of a string array, using the specified separator between each element.
Join(String, String[], Int32, Int32)	Concatenates the specified elements of a string array, using the specified separator between each element.
Join<T>(Char, IEnumerable<T>)	Concatenates the members of a collection, using the specified separator between each member.
Join<T>(String, IEnumerable<T>)	Concatenates the members of a collection, using the specified separator between each member.
LastIndexOf(Char)	Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance.
LastIndexOf(Char, Int32)	Reports the zero-based index position of the last occurrence of a specified Unicode character within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string.
LastIndexOf(Char, Int32, Int32)	Reports the zero-based index position of the last occurrence of the specified Unicode character in a substring within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.
LastIndexOf(String)	Reports the zero-based index position of the last occurrence of a specified string within this instance.
LastIndexOf(String, Int32)	Reports the zero-based index position of the last occurrence of a specified string within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string.
LastIndexOf(String, Int32, Int32)	Reports the zero-based index position of the last occurrence of a specified string within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.
LastIndexOf(String, Int32, Int32, StringComparison)	Reports the zero-based index position of the last occurrence of a specified string within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string for the specified number of character positions. A parameter specifies the type of comparison to perform when searching for the specified string.
LastIndexOf(String, Int32, StringComparison)	Reports the zero-based index of the last occurrence of a specified string within the current String object. The search starts at a specified character position and proceeds backward toward the beginning of the string. A parameter specifies the type of comparison to perform when searching for the specified string.
LastIndexOf(String, StringComparison)	Reports the zero-based index of the last occurrence of a specified string within the current String object. A parameter specifies the type of search to use for the specified string.
LastIndexOfAny(Char[])	Reports the zero-based index position of the last occurrence in this instance of one or more characters specified in a Unicode array.
LastIndexOfAny(Char[], Int32)	Reports the zero-based index position of the last occurrence in this instance of one or more characters specified in a Unicode array. The search starts at a specified character position and proceeds backward toward the beginning of the string.
LastIndexOfAny(Char[], Int32, Int32)	Reports the zero-based index position of the last occurrence in this instance of one or more characters specified in a Unicode array. The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
Normalize()	Returns a new string whose textual value is the same as this string, but whose binary representation is in Unicode normalization form C.
Normalize(NormalizationForm)	Returns a new string whose textual value is the same as this string, but whose binary representation is in the specified Unicode normalization form.
PadLeft(Int32)	Returns a new string that right-aligns the characters in this instance by padding them with spaces on the left, for a specified total length.
PadLeft(Int32, Char)	Returns a new string that right-aligns the characters in this instance by padding them on the left with a specified Unicode character, for a specified total length.
PadRight(Int32)	Returns a new string that left-aligns the characters in this string by padding them with spaces on the right, for a specified total length.
PadRight(Int32, Char)	Returns a new string that left-aligns the characters in this string by padding them on the right with a specified Unicode character, for a specified total length.
Remove(Int32)	Returns a new string in which all the characters in the current instance, beginning at a specified position and continuing through the last position, have been deleted.
Remove(Int32, Int32)	Returns a new string in which a specified number of characters in the current instance beginning at a specified position have been deleted.
Replace(Char, Char)	Returns a new string in which all occurrences of a specified Unicode character in this instance are replaced with another specified Unicode character.
Replace(String, String)	Returns a new string in which all occurrences of a specified string in the current instance are replaced with another specified string.
Replace(String, String, Boolean, CultureInfo)	Returns a new string in which all occurrences of a specified string in the current instance are replaced with another specified string, using the provided culture and case sensitivity.
Replace(String, String, StringComparison)	Returns a new string in which all occurrences of a specified string in the current instance are replaced with another specified string, using the provided comparison type.
ReplaceLineEndings()	Replaces all newline sequences in the current string with NewLine.
ReplaceLineEndings(String)	Replaces all newline sequences in the current string with `replacementText`.
Split(Char, Int32, StringSplitOptions)	Splits a string into a maximum number of substrings based on a specified delimiting character and, optionally, options. Splits a string into a maximum number of substrings based on the provided character separator, optionally omitting empty substrings from the result.
Split(Char, StringSplitOptions)	Splits a string into substrings based on a specified delimiting character and, optionally, options.
Split(Char[])	Splits a string into substrings based on specified delimiting characters.
Split(Char[], Int32)	Splits a string into a maximum number of substrings based on specified delimiting characters.
Split(Char[], Int32, StringSplitOptions)	Splits a string into a maximum number of substrings based on specified delimiting characters and, optionally, options.
Split(Char[], StringSplitOptions)	Splits a string into substrings based on specified delimiting characters and options.
Split(String, Int32, StringSplitOptions)	Splits a string into a maximum number of substrings based on a specified delimiting string and, optionally, options.
Split(String, StringSplitOptions)	Splits a string into substrings that are based on the provided string separator.
Split(String[], Int32, StringSplitOptions)	Splits a string into a maximum number of substrings based on specified delimiting strings and, optionally, options.
Split(String[], StringSplitOptions)	Splits a string into substrings based on a specified delimiting string and, optionally, options.
StartsWith(Char)	Determines whether this string instance starts with the specified character.
StartsWith(String)	Determines whether the beginning of this string instance matches the specified string.
StartsWith(String, Boolean, CultureInfo)	Determines whether the beginning of this string instance matches the specified string when compared using the specified culture.
StartsWith(String, StringComparison)	Determines whether the beginning of this string instance matches the specified string when compared using the specified comparison option.
Substring(Int32)	Retrieves a substring from this instance. The substring starts at a specified character position and continues to the end of the string.
Substring(Int32, Int32)	Retrieves a substring from this instance. The substring starts at a specified character position and has a specified length.
ToCharArray()	Copies the characters in this instance to a Unicode character array.
ToCharArray(Int32, Int32)	Copies the characters in a specified substring in this instance to a Unicode character array.
ToLower()	Returns a copy of this string converted to lowercase.
ToLower(CultureInfo)	Returns a copy of this string converted to lowercase, using the casing rules of the specified culture.
ToLowerInvariant()	Returns a copy of this String object converted to lowercase using the casing rules of the invariant culture.
ToString()	Returns this instance of String; no actual conversion is performed.
ToString(IFormatProvider)	Returns this instance of String; no actual conversion is performed.
ToUpper()	Returns a copy of this string converted to uppercase.
ToUpper(CultureInfo)	Returns a copy of this string converted to uppercase, using the casing rules of the specified culture.
ToUpperInvariant()	Returns a copy of this String object converted to uppercase using the casing rules of the invariant culture.
Trim()	Removes all leading and trailing white-space characters from the current string.
Trim(Char)	Removes all leading and trailing instances of a character from the current string.
Trim(Char[])	Removes all leading and trailing occurrences of a set of characters specified in an array from the current string.
TrimEnd()	Removes all the trailing white-space characters from the current string.
TrimEnd(Char)	Removes all the trailing occurrences of a character from the current string.
TrimEnd(Char[])	Removes all the trailing occurrences of a set of characters specified in an array from the current string.
TrimStart()	Removes all the leading white-space characters from the current string.
TrimStart(Char)	Removes all the leading occurrences of a specified character from the current string.
TrimStart(Char[])	Removes all the leading occurrences of a set of characters specified in an array from the current string.
TryCopyTo(Span<Char>)	Copies the contents of this string into the destination span.

Operators

Equality(String, String)	Determines whether two specified strings have the same value.
Implicit(String to ReadOnlySpan<Char>)	Defines an implicit conversion of a given string to a read-only span of characters.
Inequality(String, String)	Determines whether two specified strings have different values.

Explicit Interface Implementations

IComparable.CompareTo(Object)	Compares this instance with a specified Object and indicates whether this instance precedes, follows, or appears in the same position in the sort order as the specified Object.
IConvertible.GetTypeCode()	Returns the TypeCode for the String class.
IConvertible.ToBoolean(IFormatProvider)	For a description of this member, see ToBoolean(IFormatProvider).
IConvertible.ToByte(IFormatProvider)	For a description of this member, see ToByte(IFormatProvider).
IConvertible.ToChar(IFormatProvider)	For a description of this member, see ToChar(IFormatProvider).
IConvertible.ToDateTime(IFormatProvider)	For a description of this member, see ToDateTime(IFormatProvider).
IConvertible.ToDecimal(IFormatProvider)	For a description of this member, see ToDecimal(IFormatProvider).
IConvertible.ToDouble(IFormatProvider)	For a description of this member, see ToDouble(IFormatProvider).
IConvertible.ToInt16(IFormatProvider)	For a description of this member, see ToInt16(IFormatProvider).
IConvertible.ToInt32(IFormatProvider)	For a description of this member, see ToInt32(IFormatProvider).
IConvertible.ToInt64(IFormatProvider)	For a description of this member, see ToInt64(IFormatProvider).
IConvertible.ToSByte(IFormatProvider)	For a description of this member, see ToSByte(IFormatProvider).
IConvertible.ToSingle(IFormatProvider)	For a description of this member, see ToSingle(IFormatProvider).
IConvertible.ToString(IFormatProvider)	For a description of this member, see ToString(IFormatProvider).
IConvertible.ToType(Type, IFormatProvider)	For a description of this member, see ToType(Type, IFormatProvider).
IConvertible.ToUInt16(IFormatProvider)	For a description of this member, see ToUInt16(IFormatProvider).
IConvertible.ToUInt32(IFormatProvider)	For a description of this member, see ToUInt32(IFormatProvider).
IConvertible.ToUInt64(IFormatProvider)	For a description of this member, see ToUInt64(IFormatProvider).
IEnumerable.GetEnumerator()	Returns an enumerator that iterates through the current String object.
IEnumerable<Char>.GetEnumerator()	Returns an enumerator that iterates through the current String object.
IParsable<String>.Parse(String, IFormatProvider)	Parses a string into a value.
IParsable<String>.TryParse(String, IFormatProvider, String)
ISpanParsable<String>.Parse(ReadOnlySpan<Char>, IFormatProvider)	Parses a span of characters into a value.
ISpanParsable<String>.TryParse(ReadOnlySpan<Char>, IFormatProvider, String)

Extension Methods

ToFrozenDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a FrozenDictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector function.
ToFrozenDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a FrozenDictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.
ToFrozenSet<T>(IEnumerable<T>, IEqualityComparer<T>)	Creates a FrozenSet<T> with the specified values.
ToImmutableArray<TSource>(IEnumerable<TSource>)	Creates an immutable array from the specified collection.
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Constructs an immutable dictionary from an existing collection of elements, applying a transformation function to the source keys.
ToImmutableDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Constructs an immutable dictionary based on some transformation of a sequence.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key comparer.
ToImmutableDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IEqualityComparer<TKey>, IEqualityComparer<TValue>)	Enumerates and transforms a sequence, and produces an immutable dictionary of its contents by using the specified key and value comparers.
ToImmutableHashSet<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable hash set of its contents.
ToImmutableHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Enumerates a sequence, produces an immutable hash set of its contents, and uses the specified equality comparer for the set type.
ToImmutableList<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable list of its contents.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key comparer.
ToImmutableSortedDictionary<TSource,TKey,TValue>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TValue>, IComparer<TKey>, IEqualityComparer<TValue>)	Enumerates and transforms a sequence, and produces an immutable sorted dictionary of its contents by using the specified key and value comparers.
ToImmutableSortedSet<TSource>(IEnumerable<TSource>)	Enumerates a sequence and produces an immutable sorted set of its contents.
ToImmutableSortedSet<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Enumerates a sequence, produces an immutable sorted set of its contents, and uses the specified comparer.
CopyToDataTable<T>(IEnumerable<T>)	Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object where the generic parameter `T` is DataRow.
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption)	Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter `T` is DataRow.
CopyToDataTable<T>(IEnumerable<T>, DataTable, LoadOption, FillErrorEventHandler)	Copies DataRow objects to the specified DataTable, given an input IEnumerable<T> object where the generic parameter `T` is DataRow.
Aggregate<TSource>(IEnumerable<TSource>, Func<TSource,TSource,TSource>)	Applies an accumulator function over a sequence.
Aggregate<TSource,TAccumulate>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>)	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value.
Aggregate<TSource,TAccumulate,TResult>(IEnumerable<TSource>, TAccumulate, Func<TAccumulate,TSource,TAccumulate>, Func<TAccumulate,TResult>)	Applies an accumulator function over a sequence. The specified seed value is used as the initial accumulator value, and the specified function is used to select the result value.
All<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Determines whether all elements of a sequence satisfy a condition.
Any<TSource>(IEnumerable<TSource>)	Determines whether a sequence contains any elements.
Any<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Determines whether any element of a sequence satisfies a condition.
Append<TSource>(IEnumerable<TSource>, TSource)	Appends a value to the end of the sequence.
AsEnumerable<TSource>(IEnumerable<TSource>)	Returns the input typed as IEnumerable<T>.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Computes the average of a sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Computes the average of a sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Computes the average of a sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Computes the average of a sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Computes the average of a sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Computes the average of a sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Computes the average of a sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Computes the average of a sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Computes the average of a sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.
Average<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Computes the average of a sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.
Cast<TResult>(IEnumerable)	Casts the elements of an IEnumerable to the specified type.
Chunk<TSource>(IEnumerable<TSource>, Int32)	Splits the elements of a sequence into chunks of size at most `size`.
Concat<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Concatenates two sequences.
Contains<TSource>(IEnumerable<TSource>, TSource)	Determines whether a sequence contains a specified element by using the default equality comparer.
Contains<TSource>(IEnumerable<TSource>, TSource, IEqualityComparer<TSource>)	Determines whether a sequence contains a specified element by using a specified IEqualityComparer<T>.
Count<TSource>(IEnumerable<TSource>)	Returns the number of elements in a sequence.
Count<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns a number that represents how many elements in the specified sequence satisfy a condition.
DefaultIfEmpty<TSource>(IEnumerable<TSource>)	Returns the elements of the specified sequence or the type parameter's default value in a singleton collection if the sequence is empty.
DefaultIfEmpty<TSource>(IEnumerable<TSource>, TSource)	Returns the elements of the specified sequence or the specified value in a singleton collection if the sequence is empty.
Distinct<TSource>(IEnumerable<TSource>)	Returns distinct elements from a sequence by using the default equality comparer to compare values.
Distinct<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Returns distinct elements from a sequence by using a specified IEqualityComparer<T> to compare values.
DistinctBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns distinct elements from a sequence according to a specified key selector function.
DistinctBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Returns distinct elements from a sequence according to a specified key selector function and using a specified comparer to compare keys.
ElementAt<TSource>(IEnumerable<TSource>, Index)	Returns the element at a specified index in a sequence.
ElementAt<TSource>(IEnumerable<TSource>, Int32)	Returns the element at a specified index in a sequence.
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Index)	Returns the element at a specified index in a sequence or a default value if the index is out of range.
ElementAtOrDefault<TSource>(IEnumerable<TSource>, Int32)	Returns the element at a specified index in a sequence or a default value if the index is out of range.
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set difference of two sequences by using the default equality comparer to compare values.
Except<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set difference of two sequences by using the specified IEqualityComparer<T> to compare values.
ExceptBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>)	Produces the set difference of two sequences according to a specified key selector function.
ExceptBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set difference of two sequences according to a specified key selector function.
First<TSource>(IEnumerable<TSource>)	Returns the first element of a sequence.
First<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the first element in a sequence that satisfies a specified condition.
FirstOrDefault<TSource>(IEnumerable<TSource>)	Returns the first element of a sequence, or a default value if the sequence contains no elements.
FirstOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the first element of a sequence, or a specified default value if the sequence contains no elements.
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the first element of the sequence that satisfies a condition or a default value if no such element is found.
FirstOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the first element of the sequence that satisfies a condition, or a specified default value if no such element is found.
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Groups the elements of a sequence according to a specified key selector function.
GroupBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and compares the keys by using a specified comparer.
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Groups the elements of a sequence according to a specified key selector function and projects the elements for each group by using a specified function.
GroupBy<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a key selector function. The keys are compared by using a comparer and each group's elements are projected by using a specified function.
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key.
GroupBy<TSource,TKey,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TKey,IEnumerable<TSource>,TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The keys are compared by using a specified comparer.
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>,TResult>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. The elements of each group are projected by using a specified function.
GroupBy<TSource,TKey,TElement,TResult>(IEnumerable<TSource>, Func<TSource, TKey>, Func<TSource,TElement>, Func<TKey,IEnumerable<TElement>, TResult>, IEqualityComparer<TKey>)	Groups the elements of a sequence according to a specified key selector function and creates a result value from each group and its key. Key values are compared by using a specified comparer, and the elements of each group are projected by using a specified function.
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>, TResult>)	Correlates the elements of two sequences based on equality of keys and groups the results. The default equality comparer is used to compare keys.
GroupJoin<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,IEnumerable<TInner>, TResult>, IEqualityComparer<TKey>)	Correlates the elements of two sequences based on key equality and groups the results. A specified IEqualityComparer<T> is used to compare keys.
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set intersection of two sequences by using the default equality comparer to compare values.
Intersect<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set intersection of two sequences by using the specified IEqualityComparer<T> to compare values.
IntersectBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>)	Produces the set intersection of two sequences according to a specified key selector function.
IntersectBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TKey>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set intersection of two sequences according to a specified key selector function.
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>)	Correlates the elements of two sequences based on matching keys. The default equality comparer is used to compare keys.
Join<TOuter,TInner,TKey,TResult>(IEnumerable<TOuter>, IEnumerable<TInner>, Func<TOuter,TKey>, Func<TInner,TKey>, Func<TOuter,TInner,TResult>, IEqualityComparer<TKey>)	Correlates the elements of two sequences based on matching keys. A specified IEqualityComparer<T> is used to compare keys.
Last<TSource>(IEnumerable<TSource>)	Returns the last element of a sequence.
Last<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the last element of a sequence that satisfies a specified condition.
LastOrDefault<TSource>(IEnumerable<TSource>)	Returns the last element of a sequence, or a default value if the sequence contains no elements.
LastOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the last element of a sequence, or a specified default value if the sequence contains no elements.
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
LastOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the last element of a sequence that satisfies a condition, or a specified default value if no such element is found.
LongCount<TSource>(IEnumerable<TSource>)	Returns an Int64 that represents the total number of elements in a sequence.
LongCount<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns an Int64 that represents how many elements in a sequence satisfy a condition.
Max<TSource>(IEnumerable<TSource>)	Returns the maximum value in a generic sequence.
Max<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Returns the maximum value in a generic sequence.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Invokes a transform function on each element of a sequence and returns the maximum Decimal value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Invokes a transform function on each element of a sequence and returns the maximum Double value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Invokes a transform function on each element of a sequence and returns the maximum Int32 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Invokes a transform function on each element of a sequence and returns the maximum Int64 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Decimal value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Double value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Int32 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Int64 value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Invokes a transform function on each element of a sequence and returns the maximum nullable Single value.
Max<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Invokes a transform function on each element of a sequence and returns the maximum Single value.
Max<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Invokes a transform function on each element of a generic sequence and returns the maximum resulting value.
MaxBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns the maximum value in a generic sequence according to a specified key selector function.
MaxBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Returns the maximum value in a generic sequence according to a specified key selector function and key comparer.
Min<TSource>(IEnumerable<TSource>)	Returns the minimum value in a generic sequence.
Min<TSource>(IEnumerable<TSource>, IComparer<TSource>)	Returns the minimum value in a generic sequence.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Invokes a transform function on each element of a sequence and returns the minimum Decimal value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Invokes a transform function on each element of a sequence and returns the minimum Double value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Invokes a transform function on each element of a sequence and returns the minimum Int32 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Invokes a transform function on each element of a sequence and returns the minimum Int64 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Decimal value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Double value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Int32 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Int64 value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Invokes a transform function on each element of a sequence and returns the minimum nullable Single value.
Min<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Invokes a transform function on each element of a sequence and returns the minimum Single value.
Min<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Invokes a transform function on each element of a generic sequence and returns the minimum resulting value.
MinBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Returns the minimum value in a generic sequence according to a specified key selector function.
MinBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Returns the minimum value in a generic sequence according to a specified key selector function and key comparer.
OfType<TResult>(IEnumerable)	Filters the elements of an IEnumerable based on a specified type.
Order<T>(IEnumerable<T>)	Sorts the elements of a sequence in ascending order.
Order<T>(IEnumerable<T>, IComparer<T>)	Sorts the elements of a sequence in ascending order.
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Sorts the elements of a sequence in ascending order according to a key.
OrderBy<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Sorts the elements of a sequence in ascending order by using a specified comparer.
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Sorts the elements of a sequence in descending order according to a key.
OrderByDescending<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IComparer<TKey>)	Sorts the elements of a sequence in descending order by using a specified comparer.
OrderDescending<T>(IEnumerable<T>)	Sorts the elements of a sequence in descending order.
OrderDescending<T>(IEnumerable<T>, IComparer<T>)	Sorts the elements of a sequence in descending order.
Prepend<TSource>(IEnumerable<TSource>, TSource)	Adds a value to the beginning of the sequence.
Reverse<TSource>(IEnumerable<TSource>)	Inverts the order of the elements in a sequence.
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,TResult>)	Projects each element of a sequence into a new form.
Select<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,TResult>)	Projects each element of a sequence into a new form by incorporating the element's index.
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TResult>>)	Projects each element of a sequence to an IEnumerable<T> and flattens the resulting sequences into one sequence.
SelectMany<TSource,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TResult>>)	Projects each element of a sequence to an IEnumerable<T>, and flattens the resulting sequences into one sequence. The index of each source element is used in the projected form of that element.
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)	Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein.
SelectMany<TSource,TCollection,TResult>(IEnumerable<TSource>, Func<TSource,Int32,IEnumerable<TCollection>>, Func<TSource,TCollection,TResult>)	Projects each element of a sequence to an IEnumerable<T>, flattens the resulting sequences into one sequence, and invokes a result selector function on each element therein. The index of each source element is used in the intermediate projected form of that element.
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Determines whether two sequences are equal by comparing the elements by using the default equality comparer for their type.
SequenceEqual<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Determines whether two sequences are equal by comparing their elements by using a specified IEqualityComparer<T>.
Single<TSource>(IEnumerable<TSource>)	Returns the only element of a sequence, and throws an exception if there is not exactly one element in the sequence.
Single<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the only element of a sequence that satisfies a specified condition, and throws an exception if more than one such element exists.
SingleOrDefault<TSource>(IEnumerable<TSource>)	Returns the only element of a sequence, or a default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
SingleOrDefault<TSource>(IEnumerable<TSource>, TSource)	Returns the only element of a sequence, or a specified default value if the sequence is empty; this method throws an exception if there is more than one element in the sequence.
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns the only element of a sequence that satisfies a specified condition or a default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
SingleOrDefault<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>, TSource)	Returns the only element of a sequence that satisfies a specified condition, or a specified default value if no such element exists; this method throws an exception if more than one element satisfies the condition.
Skip<TSource>(IEnumerable<TSource>, Int32)	Bypasses a specified number of elements in a sequence and then returns the remaining elements.
SkipLast<TSource>(IEnumerable<TSource>, Int32)	Returns a new enumerable collection that contains the elements from `source` with the last `count` elements of the source collection omitted.
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements.
SkipWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Bypasses elements in a sequence as long as a specified condition is true and then returns the remaining elements. The element's index is used in the logic of the predicate function.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Decimal>)	Computes the sum of the sequence of Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Double>)	Computes the sum of the sequence of Double values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int32>)	Computes the sum of the sequence of Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Int64>)	Computes the sum of the sequence of Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Decimal>>)	Computes the sum of the sequence of nullable Decimal values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Double>>)	Computes the sum of the sequence of nullable Double values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int32>>)	Computes the sum of the sequence of nullable Int32 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Int64>>)	Computes the sum of the sequence of nullable Int64 values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Nullable<Single>>)	Computes the sum of the sequence of nullable Single values that are obtained by invoking a transform function on each element of the input sequence.
Sum<TSource>(IEnumerable<TSource>, Func<TSource,Single>)	Computes the sum of the sequence of Single values that are obtained by invoking a transform function on each element of the input sequence.
Take<TSource>(IEnumerable<TSource>, Int32)	Returns a specified number of contiguous elements from the start of a sequence.
Take<TSource>(IEnumerable<TSource>, Range)	Returns a specified range of contiguous elements from a sequence.
TakeLast<TSource>(IEnumerable<TSource>, Int32)	Returns a new enumerable collection that contains the last `count` elements from `source`.
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Returns elements from a sequence as long as a specified condition is true.
TakeWhile<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Returns elements from a sequence as long as a specified condition is true. The element's index is used in the logic of the predicate function.
ToArray<TSource>(IEnumerable<TSource>)	Creates an array from a IEnumerable<T>.
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function.
ToDictionary<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function and key comparer.
ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to specified key selector and element selector functions.
ToDictionary<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a Dictionary<TKey,TValue> from an IEnumerable<T> according to a specified key selector function, a comparer, and an element selector function.
ToHashSet<TSource>(IEnumerable<TSource>)	Creates a HashSet<T> from an IEnumerable<T>.
ToHashSet<TSource>(IEnumerable<TSource>, IEqualityComparer<TSource>)	Creates a HashSet<T> from an IEnumerable<T> using the `comparer` to compare keys.
ToList<TSource>(IEnumerable<TSource>)	Creates a List<T> from an IEnumerable<T>.
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function.
ToLookup<TSource,TKey>(IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function and key comparer.
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to specified key selector and element selector functions.
ToLookup<TSource,TKey,TElement>(IEnumerable<TSource>, Func<TSource,TKey>, Func<TSource,TElement>, IEqualityComparer<TKey>)	Creates a Lookup<TKey,TElement> from an IEnumerable<T> according to a specified key selector function, a comparer and an element selector function.
TryGetNonEnumeratedCount<TSource>(IEnumerable<TSource>, Int32)	Attempts to determine the number of elements in a sequence without forcing an enumeration.
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>)	Produces the set union of two sequences by using the default equality comparer.
Union<TSource>(IEnumerable<TSource>, IEnumerable<TSource>, IEqualityComparer<TSource>)	Produces the set union of two sequences by using a specified IEqualityComparer<T>.
UnionBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TSource>, Func<TSource,TKey>)	Produces the set union of two sequences according to a specified key selector function.
UnionBy<TSource,TKey>(IEnumerable<TSource>, IEnumerable<TSource>, Func<TSource,TKey>, IEqualityComparer<TKey>)	Produces the set union of two sequences according to a specified key selector function.
Where<TSource>(IEnumerable<TSource>, Func<TSource,Boolean>)	Filters a sequence of values based on a predicate.
Where<TSource>(IEnumerable<TSource>, Func<TSource,Int32,Boolean>)	Filters a sequence of values based on a predicate. Each element's index is used in the logic of the predicate function.
Zip<TFirst,TSecond>(IEnumerable<TFirst>, IEnumerable<TSecond>)	Produces a sequence of tuples with elements from the two specified sequences.
Zip<TFirst,TSecond,TThird>(IEnumerable<TFirst>, IEnumerable<TSecond>, IEnumerable<TThird>)	Produces a sequence of tuples with elements from the three specified sequences.
Zip<TFirst,TSecond,TResult>(IEnumerable<TFirst>, IEnumerable<TSecond>, Func<TFirst,TSecond,TResult>)	Applies a specified function to the corresponding elements of two sequences, producing a sequence of the results.
AsParallel(IEnumerable)	Enables parallelization of a query.
AsParallel<TSource>(IEnumerable<TSource>)	Enables parallelization of a query.
AsQueryable(IEnumerable)	Converts an IEnumerable to an IQueryable.
AsQueryable<TElement>(IEnumerable<TElement>)	Converts a generic IEnumerable<T> to a generic IQueryable<T>.
AsMemory(String)	Creates a new `ReadOnlyMemory<Char>` over the portion of the target string.
AsMemory(String, Index)	Creates a new `ReadOnlyMemory<Char>` over a portion of the target string starting at a specified index.
AsMemory(String, Int32)	Creates a new `ReadOnlyMemory<Char>` over a portion of the target string starting at a specified character position.
AsMemory(String, Int32, Int32)	Creates a new `ReadOnlyMemory<Char>` over a portion of the target string beginning at a specified position with a length.
AsMemory(String, Range)	Creates a new `ReadOnlyMemory<Char>` over a specified range of the target string.
AsSpan(String)	Creates a new read-only span over a string.
AsSpan(String, Index)	Creates a new ReadOnlySpan<T> over a portion of the target string from a specified position to the end of the string.
AsSpan(String, Int32)	Creates a new read-only span over a portion of the target string from a specified position to the end of the string.
AsSpan(String, Int32, Int32)	Creates a new read-only span over a portion of the target string from a specified position for a specified number of characters.
AsSpan(String, Range)	Creates a new ReadOnlySpan<T> over a portion of a target string using the range start and end indexes.
IsNormalized(String)	Indicates whether the specified string is in Unicode normalization form C.
IsNormalized(String, NormalizationForm)	Indicates whether a string is in a specified Unicode normalization form.
Normalize(String)	Normalizes a string to a Unicode normalization form C.
Normalize(String, NormalizationForm)	Normalizes a string to the specified Unicode normalization form.
Ancestors<T>(IEnumerable<T>)	Returns a collection of elements that contains the ancestors of every node in the source collection.
Ancestors<T>(IEnumerable<T>, XName)	Returns a filtered collection of elements that contains the ancestors of every node in the source collection. Only elements that have a matching XName are included in the collection.
DescendantNodes<T>(IEnumerable<T>)	Returns a collection of the descendant nodes of every document and element in the source collection.
Descendants<T>(IEnumerable<T>)	Returns a collection of elements that contains the descendant elements of every element and document in the source collection.
Descendants<T>(IEnumerable<T>, XName)	Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.
Elements<T>(IEnumerable<T>)	Returns a collection of the child elements of every element and document in the source collection.
Elements<T>(IEnumerable<T>, XName)	Returns a filtered collection of the child elements of every element and document in the source collection. Only elements that have a matching XName are included in the collection.
InDocumentOrder<T>(IEnumerable<T>)	Returns a collection of nodes that contains all nodes in the source collection, sorted in document order.
Nodes<T>(IEnumerable<T>)	Returns a collection of the child nodes of every document and element in the source collection.
Remove<T>(IEnumerable<T>)	Removes every node in the source collection from its parent node.

Applies to

Thread Safety

This type is thread safe.

String Class

Definition

Remarks

Instantiate a String object

Char objects and Unicode characters

Strings and the Unicode Standard

Strings and embedded null characters

Strings and indexes

Null strings and empty strings

Immutability and the StringBuilder class

Ordinal vs. culture-sensitive operations

Casing

Parsing and formatting

String comparison and sorting

Search in strings

Testing for equality

Normalization

String operations by category

Compare strings

Test strings for equality

Find characters in a string

Modify a string

Extract substrings from a string

Combine strings

Format values

Copy a string

Normalize a string

Constructors

Fields

Properties

Methods

Operators

Explicit Interface Implementations

Extension Methods

Applies to

Thread Safety

See also

Additional resources