String.Concat Method

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Concatenates one or more instances of String, or the String representations of the values of one or more instances of Object.

Overloads

Concat(String, String, String, String)	Concatenates four specified instances of String.
Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>)	Concatenates the string representations of four specified read-only character spans.
Concat(String, String, String)	Concatenates three specified instances of String.
Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>)	Concatenates the string representations of three specified read-only character spans.
Concat(Object, Object, Object)	Concatenates the string representations of three specified objects.
Concat(String, String)	Concatenates two specified instances of String.
Concat(IEnumerable<String>)	Concatenates the members of a constructed IEnumerable<T> collection of type String.
Concat(Object, Object)	Concatenates the string representations of two specified objects.
Concat(String[])	Concatenates the elements of a specified String array.
Concat(ReadOnlySpan<String>)	Concatenates the elements of a specified span of String.
Concat(ReadOnlySpan<Object>)	Concatenates the string representations of the elements in a specified span of objects.
Concat(Object[])	Concatenates the string representations of the elements in a specified Object array.
Concat(Object)	Creates the string representation of a specified object.
Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>)	Concatenates the string representations of two specified read-only character spans.
Concat<T>(IEnumerable<T>)	Concatenates the members of an IEnumerable<T> implementation.

Remarks

Note

You can also use your language's string concatenation operator, such as + in C# and F#, or & and + in Visual Basic, to concatenate strings. Both compilers translate the concatenation operator into a call to one of the overloads of String.Concat.

Concat(String, String, String, String)

Source:

String.Manipulation.cs

Concatenates four specified instances of String.

public:
 static System::String ^ Concat(System::String ^ str0, System::String ^ str1, System::String ^ str2, System::String ^ str3);

public static string Concat (string? str0, string? str1, string? str2, string? str3);

static member Concat : string * string * string * string -> string

Public Shared Function Concat (str0 As String, str1 As String, str2 As String, str3 As String) As String

Parameters

str0

String

The first string to concatenate.

str1

String

The second string to concatenate.

str2

String

The third string to concatenate.

str3

String

The fourth string to concatenate.

Returns

String

The concatenation of str0, str1, str2, and str3.

Examples

The following example defines an array of four-letter words and stores their individual letters to a string array in order to scramble them. It then calls the Concat(String, String, String, String) method to reassemble the scrambled words.

using System;
using System.Collections;

public class Example
{
   public static void Main()
   {
      const int WORD_SIZE = 4;
      
      // Define some 4-letter words to be scrambled.
      string[] words = { "home", "food", "game", "rest" };
      // Define two arrays equal to the number of letters in each word.
      double[] keys = new double[WORD_SIZE];
      string[] letters = new string[WORD_SIZE];
      // Initialize the random number generator.
      Random rnd = new Random();
      
      // Scramble each word.
      foreach (string word in words)
      {
         for (int ctr = 0; ctr < word.Length; ctr++)
         {
            // Populate the array of keys with random numbers.
            keys[ctr] = rnd.NextDouble();
            // Assign a letter to the array of letters.
            letters[ctr] = word[ctr].ToString();
         }   
         // Sort the array. 
         Array.Sort(keys, letters, 0, WORD_SIZE, Comparer.Default);      
         // Display the scrambled word.
         string scrambledWord = String.Concat(letters[0], letters[1], 
                                              letters[2], letters[3]);
         Console.WriteLine("{0} --> {1}", word, scrambledWord);
      } 
   }
}
// The example displays output like the following:
//       home --> mheo
//       food --> oodf
//       game --> aemg
//       rest --> trse

open System
open System.Collections

let WORD_SIZE = 4
      
// Define some 4-letter words to be scrambled.
let words = [| "home"; "food"; "game"; "rest" |]
// Define two arrays equal to the number of letters in each word.
let keys = Array.zeroCreate<float> WORD_SIZE
let letters = Array.zeroCreate<string> WORD_SIZE
// Initialize the random number generator.
let rnd = Random()

// Scramble each word.
for word in words do
    for i = 0 to word.Length - 1 do
        // Populate the array of keys with random numbers.
        keys[i] <- rnd.NextDouble()
        // Assign a letter to the array of letters.
        letters[i] <- string word[i]
    // Sort the array. 
    Array.Sort(keys, letters, 0, WORD_SIZE, Comparer.Default)      
    // Display the scrambled word.
    let scrambledWord = String.Concat(letters[0], letters[1], letters[2], letters[3])
    printfn $"{word} --> {scrambledWord}"
// The example displays output like the following:
//       home --> mheo
//       food --> oodf
//       game --> aemg
//       rest --> trse

Imports System.Collections

Module Example
   Public Sub Main()
      Const WORD_SIZE As Integer = 4
      
      ' Define some 4-letter words to be scrambled.
      Dim words() As String = { "home", "food", "game", "rest" }
      ' Define two arrays equal to the number of letters in each word.
      Dim keys(WORD_SIZE) As Double
      Dim letters(WORD_SIZE) As String
      ' Initialize the random number generator.
      Dim rnd As New Random()
      
      ' Scramble each word.
      For Each word As String In words
         For ctr As Integer = 0 To word.Length - 1
            ' Populate the array of keys with random numbers.
            keys(ctr) = rnd.NextDouble()
            ' Assign a letter to the array of letters.
            letters(ctr) = word.Chars(ctr)
         Next   
         ' Sort the array. 
         Array.Sort(keys, letters, 0, WORD_SIZE, Comparer.Default)      
         ' Display the scrambled word.
         Dim scrambledWord As String = String.Concat(letters(0), letters(1), _
                                                     letters(2), letters(3))
         Console.WriteLine("{0} --> {1}", word, scrambledWord)
      Next 
   End Sub
End Module 
' The example displays output like the following:
'       home --> mheo
'       food --> oodf
'       game --> aemg
'       rest --> trse

Remarks

The method concatenates str0, str1, str2, and str3; it does not add any delimiters.

See also

• Join(String, String[])

Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>)

Source:

String.Manipulation.cs

Concatenates the string representations of four specified read-only character spans.

public:
 static System::String ^ Concat(ReadOnlySpan<char> str0, ReadOnlySpan<char> str1, ReadOnlySpan<char> str2, ReadOnlySpan<char> str3);

public static string Concat (ReadOnlySpan<char> str0, ReadOnlySpan<char> str1, ReadOnlySpan<char> str2, ReadOnlySpan<char> str3);

static member Concat : ReadOnlySpan<char> * ReadOnlySpan<char> * ReadOnlySpan<char> * ReadOnlySpan<char> -> string

Public Shared Function Concat (str0 As ReadOnlySpan(Of Char), str1 As ReadOnlySpan(Of Char), str2 As ReadOnlySpan(Of Char), str3 As ReadOnlySpan(Of Char)) As String

Parameters

str0

ReadOnlySpan<Char>

The first read-only character span to concatenate.

str1

ReadOnlySpan<Char>

The second read-only character span to concatenate.

str2

ReadOnlySpan<Char>

The third read-only character span to concatenate.

str3

ReadOnlySpan<Char>

The fourth read-only character span to concatenate.

Returns

String

The concatenated string representations of the values of str0, str1, str2 and str3.

Concat(String, String, String)

Source:

String.Manipulation.cs

Concatenates three specified instances of String.

public:
 static System::String ^ Concat(System::String ^ str0, System::String ^ str1, System::String ^ str2);

public static string Concat (string? str0, string? str1, string? str2);

static member Concat : string * string * string -> string

Public Shared Function Concat (str0 As String, str1 As String, str2 As String) As String

Parameters

str0

String

The first string to concatenate.

str1

String

The second string to concatenate.

str2

String

The third string to concatenate.

Returns

String

The concatenation of str0, str1, and str2.

Examples

The following example uses the Concat method to concatenate three strings and displays the result.

using namespace System;

void main()
{
   String^ s1 = "We went to a bookstore, ";
   String^ s2 = "a movie, ";
   String^ s3 = "and a restaurant.";

   String^ s = String::Concat(s1, s2, s3);
   Console::WriteLine(s);
}
// The example displays the following output:
//      We went to a bookstore, a movie, and a restaurant.

using System;

public class Example
{
   public static void Main()
   {
      String s1 = "We went to a bookstore, ";
      String s2 = "a movie, ";
      String s3 = "and a restaurant.";

      var s = String.Concat(s1, s2, s3);
      Console.WriteLine(s);
   }
}
// The example displays the following output:
//      We went to a bookstore, a movie, and a restaurant.

open System

let s1 = "We went to a bookstore, "
let s2 = "a movie, "
let s3 = "and a restaurant."

String.Concat(s1, s2, s3)
|> printfn "%s"
// The example displays the following output:
//      We went to a bookstore, a movie, and a restaurant.

Public Module Example
   Public Sub Main()
      Dim s1 As String = "We went to a bookstore, "
      Dim s2 As String = "a movie, "
      Dim s3 As String = "and a restaurant."

      Dim s = String.Concat(s1, s2, s3)
      Console.WriteLine(s)
   End Sub
End Module
' The example displays the following output:
'      We went to a bookstore, a movie, and a restaurant.

Remarks

The method concatenates str0, str1, and str2; it does not add any delimiters.

See also

• Join(String, String[])

Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>, ReadOnlySpan<Char>)

Source:

String.Manipulation.cs

Concatenates the string representations of three specified read-only character spans.

public:
 static System::String ^ Concat(ReadOnlySpan<char> str0, ReadOnlySpan<char> str1, ReadOnlySpan<char> str2);

public static string Concat (ReadOnlySpan<char> str0, ReadOnlySpan<char> str1, ReadOnlySpan<char> str2);

static member Concat : ReadOnlySpan<char> * ReadOnlySpan<char> * ReadOnlySpan<char> -> string

Public Shared Function Concat (str0 As ReadOnlySpan(Of Char), str1 As ReadOnlySpan(Of Char), str2 As ReadOnlySpan(Of Char)) As String

Parameters

str0

ReadOnlySpan<Char>

The first read-only character span to concatenate.

str1

ReadOnlySpan<Char>

The second read-only character span to concatenate.

str2

ReadOnlySpan<Char>

The third read-only character span to concatenate.

Returns

String

The concatenated string representations of the values of str0, str1 and str2.

Concat(Object, Object, Object)

Source:

String.Manipulation.cs

Concatenates the string representations of three specified objects.

public:
 static System::String ^ Concat(System::Object ^ arg0, System::Object ^ arg1, System::Object ^ arg2);

public static string Concat (object? arg0, object? arg1, object? arg2);

static member Concat : obj * obj * obj -> string

Public Shared Function Concat (arg0 As Object, arg1 As Object, arg2 As Object) As String

Parameters

arg0

Object

The first object to concatenate.

arg1

Object

The second object to concatenate.

arg2

Object

The third object to concatenate.

Returns

String

The concatenated string representations of the values of arg0, arg1, and arg2.

Examples

The following example demonstrates the Concat method.

using namespace System;

int main()
{
   int i = -123;
   Object^ o = i;
   array<Object^>^objs = { -123, -456, -789};
   Console::WriteLine("Concatenate 1, 2, and 3 objects:");
   Console::WriteLine("1) {0}", String::Concat(o));
   Console::WriteLine("2) {0}", String::Concat(o, o));
   Console::WriteLine("3) {0}", String::Concat(o, o, o));
   
   Console::WriteLine("\nConcatenate 4 objects and a variable length parameter list:" );
   Console::WriteLine("4) {0}", String::Concat(o, o, o, o));
   Console::WriteLine("5) {0}", String::Concat( o, o, o, o, o));
   Console::WriteLine("\nConcatenate a 3-element object array:");
   Console::WriteLine("6) {0}", String::Concat(objs));
}
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//    
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//    
//    Concatenate a 3-element object array:
//    6) -123-456-789

using System;

class stringConcat5 {
    public static void Main() {
    int i = -123;
    Object o = i;
    Object[] objs = new Object[] {-123, -456, -789};

    Console.WriteLine("Concatenate 1, 2, and 3 objects:");
    Console.WriteLine("1) {0}", String.Concat(o));
    Console.WriteLine("2) {0}", String.Concat(o, o));
    Console.WriteLine("3) {0}", String.Concat(o, o, o));

    Console.WriteLine("\nConcatenate 4 objects and a variable length parameter list:");
    Console.WriteLine("4) {0}", String.Concat(o, o, o, o));
    Console.WriteLine("5) {0}", String.Concat(o, o, o, o, o));

    Console.WriteLine("\nConcatenate a 3-element object array:");
    Console.WriteLine("6) {0}", String.Concat(objs));
    }
}
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//
//    Concatenate a 3-element object array:
//    6) -123-456-789

open System

let i = -123
let o: obj = i
let objs: obj[] = [| -123; -456; -789 |]

printfn "Concatenate 1, 2, and 3 objects:"
printfn $"1) {String.Concat o}"
printfn $"2) {String.Concat(o, o)}"
printfn $"3) {String.Concat(o, o, o)}"

printfn "\nConcatenate 4 objects and a variable length parameter list:"
printfn $"4) {String.Concat(o, o, o, o)}"
printfn $"5) {String.Concat(o, o, o, o, o)}"

printfn "\nConcatenate a 3-element object array:"
printfn $"6) {String.Concat objs}" 
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//
//    Concatenate a 3-element object array:
//    6) -123-456-789

Class stringConcat5
   Public Shared Sub Main()
      Dim i As Integer = - 123
      Dim o As [Object] = i
      Dim objs() As [Object] = {-123, -456, -789}
      
      Console.WriteLine("Concatenate 1, 2, and 3 objects:")
      Console.WriteLine("1) {0}", [String].Concat(o))
      Console.WriteLine("2) {0}", [String].Concat(o, o))
      Console.WriteLine("3) {0}", [String].Concat(o, o, o))
      
      Console.WriteLine(vbCrLf & "Concatenate 4 objects and a variable length parameter list:")
      Console.WriteLine("4) {0}", String.Concat(o, o, o, o))
      Console.WriteLine("5) {0}", String.Concat(o, o, o, o, o))
      
      Console.WriteLine(vbCrLf & "Concatenate a 3-element object array:")
      Console.WriteLine("6) {0}", [String].Concat(objs))
   End Sub
End Class
'The example displays the following output:
'    Concatenate 1, 2, and 3 objects:
'    1) -123
'    2) -123-123
'    3) -123-123-123
'    
'    Concatenate 4 objects and a variable length parameter list:
'    4) -123-123-123-123
'    5) -123-123-123-123-123
'         
'    Concatenate a 3-element object array:
'    6) -123-456-789

Remarks

The method concatenates arg0, arg1, and arg2 by calling the parameterless ToString method of each object; it does not add any delimiters.

String.Empty is used in place of any null argument.

See also

• Object
• Join(String, String[])

Concat(String, String)

Source:

String.Manipulation.cs

Concatenates two specified instances of String.

public:
 static System::String ^ Concat(System::String ^ str0, System::String ^ str1);

public static string Concat (string? str0, string? str1);

static member Concat : string * string -> string

Public Shared Function Concat (str0 As String, str1 As String) As String

Parameters

str0

String

The first string to concatenate.

str1

String

The second string to concatenate.

Returns

String

The concatenation of str0 and str1.

Examples

The following example concatenates a person's first, middle, and last name.

using namespace System;
int main()
{
   
   // we want to simply quickly add this person's name together
   String^ fName = "Simon";
   String^ mName = "Jake";
   String^ lName = "Harrows";
   
   // because we want a name to appear with a space in between each name, 
   // put a space on the front of the middle, and last name, allowing for
   // the fact that a space may already be there
   mName = String::Concat(  " ", mName->Trim() );
   lName = String::Concat(  " ", lName->Trim() );
   
   // this line simply concatenates the two strings
   Console::WriteLine( "Welcome to this page, '{0}'!", String::Concat( String::Concat( fName, mName ), lName ) );
}
// The example displays the following output:
//        Welcome to this page, 'Simon Jake Harrows'!

using System;

public class ConcatTest {
    public static void Main() {

        // we want to simply quickly add this person's name together
        string fName = "Simon";
        string mName = "Jake";
        string lName = "Harrows";

        // because we want a name to appear with a space in between each name,
        // put a space on the front of the middle, and last name, allowing for
        // the fact that a space may already be there
        mName = " " + mName.Trim();
        lName = " " + lName.Trim();

        // this line simply concatenates the two strings
        Console.WriteLine("Welcome to this page, '{0}'!", string.Concat( string.Concat(fName, mName), lName ) );
    }
}
// The example displays the following output:
//        Welcome to this page, 'Simon Jake Harrows'!

open System

[<EntryPoint>]
let main _ =
    // we want to simply quickly add this person's name together
    let fName = "Simon"
    let mName = "Jake"
    let lName = "Harrows"

    // because we want a name to appear with a space in between each name,
    // put a space on the front of the middle, and last name, allowing for
    // the fact that a space may already be there
    let mName = " " + mName.Trim()
    let lName = " " + lName.Trim()

    // this line simply concatenates the two strings
    printfn $"Welcome to this page, '{String.Concat(String.Concat(fName, mName), lName)}'!"
    0
// The example displays the following output:
//        Welcome to this page, 'Simon Jake Harrows'!

Public Class ConcatTest
    Public Shared Sub Main()
        Dim fName As String = "Simon"
        Dim mName As String = "Jake"
        Dim lName As String = "Harrows"
        
        ' We want to simply quickly add this person's name together.
        ' Because we want a name to appear with a space in between each name, 
        ' we put a space on the front of the middle, and last name, allowing for
        ' the fact that a space may already be there.
        mName = " " + mName.Trim()
        lName = " " + lName.Trim()
        
        ' This line simply concatenates the two strings.
        Console.WriteLine("Welcome to this page, '{0}'!", _
                          String.Concat(String.Concat(fName, mName), lName))
    End Sub
End Class
' The example displays the following output:
'       Welcome to this page, 'Simon Jake Harrows'!

Remarks

The method concatenates str0 and str1; it does not add any delimiters.

An Empty string is used in place of any null argument.

See also

• Join(String, String[])

Concat(IEnumerable<String>)

Source:

String.Manipulation.cs

Concatenates the members of a constructed IEnumerable<T> collection of type String.

public:
 static System::String ^ Concat(System::Collections::Generic::IEnumerable<System::String ^> ^ values);

public static string Concat (System.Collections.Generic.IEnumerable<string?> values);

static member Concat : seq<string> -> string

Public Shared Function Concat (values As IEnumerable(Of String)) As String

Parameters

values

IEnumerable<String>

A collection object that implements IEnumerable<T> and whose generic type argument is String.

Returns

String

The concatenated strings in values, or Empty if values is an empty IEnumerable(Of String).

Exceptions

ArgumentNullException

values is null.

Examples

The following example uses the Sieve of Eratosthenes algorithm to calculate the prime numbers that are less than or equal to 100. It assigns the result to a List<T> object of type String, which it then passes to the Concat(IEnumerable<String>) method.

using System;
using System.Collections.Generic;

public class Example
{
   public static void Main()
   {
      int maxPrime = 100;
      IEnumerable<String> primeList = GetPrimes(maxPrime);
      Console.WriteLine("Primes less than {0}:", maxPrime);
      Console.WriteLine("   {0}", String.Concat(primeList));
   }

   private static IEnumerable<String> GetPrimes(int maxPrime)
   {
      Array values = Array.CreateInstance(typeof(int), 
                              new int[] { maxPrime - 1}, new int[] { 2 }); 
      // Use Sieve of Erathsthenes to determine prime numbers.
      for (int ctr = values.GetLowerBound(0); ctr <= (int) Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))); ctr++)
      {
                           
         if ((int) values.GetValue(ctr) == 1) continue;
         
         for (int multiplier = ctr; multiplier <=  maxPrime / 2; multiplier++)
            if (ctr * multiplier <= maxPrime)
               values.SetValue(1, ctr * multiplier);
      }      
      
      List<String> primes = new List<String>();
      for (int ctr = values.GetLowerBound(0); ctr <= values.GetUpperBound(0); ctr++)
         if ((int) values.GetValue(ctr) == 0) 
            primes.Add(ctr.ToString() + " ");
      return primes;
   }   
}
// The example displays the following output:
//    Primes less than 100:
//       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

open System

let getPrimes maxPrime =
    let values = Array.CreateInstance(typeof<int>, [| maxPrime - 1|], [| 2 |]) 
    // Use Sieve of Erathsthenes to determine prime numbers.
    for i = values.GetLowerBound 0 to values.GetUpperBound 0 |> float |> sqrt |> ceil |> int do
        if values.GetValue i :?> int <> 1 then
            for multiplier = i to maxPrime / 2 do
                if i * multiplier <= maxPrime then
                    values.SetValue(1, i * multiplier)
    seq {
        for i = values.GetLowerBound 0 to values.GetUpperBound 0 do
            if values.GetValue i :?> int = 0 then
                string i + " "
    }    

let maxPrime = 100
let primeList = getPrimes maxPrime
printfn $"Primes less than {maxPrime}:"
printfn $"   {String.Concat primeList}"

// The example displays the following output:
//    Primes less than 100:
//       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

Imports System.Collections.Generic

Module Example
   Public Sub Main()
      Dim maxPrime As Integer = 100
      Dim primeList As IEnumerable(Of String) = GetPrimes(maxPrime)
      Console.WriteLine("Primes less than {0}:", maxPrime)
      Console.WriteLine("   {0}", String.Concat(primeList))
   End Sub
   
   Private Function GetPrimes(maxPrime As Integer) As IEnumerable(Of String)
      Dim values As Array = Array.CreateInstance(GetType(Integer), _
                              New Integer() { maxPrime - 1}, New Integer(){ 2 }) 
      ' Use Sieve of Erathsthenes to determine prime numbers.
      For ctr As Integer = values.GetLowerBound(0) To _
                           CInt(Math.Ceiling(Math.Sqrt(values.GetUpperBound(0))))
         If CInt(values.GetValue(ctr)) = 1 Then Continue For
         
         For multiplier As Integer = ctr To maxPrime \ 2
            If ctr * multiplier <= maxPrime Then values.SetValue(1, ctr * multiplier)
         Next   
      Next      
      
      Dim primes As New List(Of String)
      For ctr As Integer = values.GetLowerBound(0) To values.GetUpperBound(0)
         If CInt(values.GetValue(ctr)) = 0 Then primes.Add(ctr.ToString() + " ")
      Next            
      Return primes
   End Function   
End Module
' The example displays the following output:
'    Primes less than 100:
'       2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97

Remarks

The method concatenates each object in values; it does not add any delimiters. To specify a delimiter between each member of values, call the Join(String, IEnumerable<String>) method.

An Empty string is used in place of any null element in values.

If values is an empty IEnumerable(Of String), the method returns String.Empty. If values is null, the method throws an ArgumentNullException exception.

Concat(IEnumerable<String>) is a convenience method that lets you concatenate each element in an IEnumerable(Of String) collection without first converting the elements to a string array. It is particularly useful with Language-Integrated Query (LINQ) query expressions. The following example passes a List(Of String) object that contains either the uppercase or lowercase letters of the alphabet to a lambda expression that selects letters that are equal to or greater than a particular letter (which, in the example, is "M"). The IEnumerable(Of String) collection that is returned by the Enumerable.Where method is passed to the Concat(IEnumerable<String>) method to display the result as a single string.

using System;
using System.Collections.Generic;
using System.Linq;

public class Example
{
   public static void Main()
   {
      string output = String.Concat( GetAlphabet(true).Where( letter => 
                      letter.CompareTo("M") >= 0));
      Console.WriteLine(output);  
   }

   private static List<string> GetAlphabet(bool upper)
   {
      List<string> alphabet = new List<string>();
      int charValue = upper ? 65 : 97;
      for (int ctr = 0; ctr <= 25; ctr++)
         alphabet.Add(((char)(charValue + ctr)).ToString());
      return alphabet; 
   }
}
// The example displays the following output:
//      MNOPQRSTUVWXYZ

// This example uses the F# Seq.filter function instead of Linq.
open System

let getAlphabet upper =
    let charValue = if upper then 65 else 97
    seq {
        for i = 0 to 25 do
            charValue + i |> char |> string
    }

getAlphabet true
|> Seq.filter (fun letter -> letter.CompareTo "M" >= 0)
|> String.Concat
|> printfn "%s"
// The example displays the following output:
//      MNOPQRSTUVWXYZ

Imports System.Collections.Generic
Imports System.Linq

Module modMain
   Public Sub Main()
      Dim output As String = String.Concat(GetAlphabet(true).Where(Function(letter) _
                                                         letter >= "M"))
        
      Console.WriteLine(output)                                     
   End Sub
   
   Private Function GetAlphabet(upper As Boolean) As List(Of String)
      Dim alphabet As New List(Of String)
      Dim charValue As Integer = CInt(IIf(upper, 65, 97))
      For ctr As Integer = 0 To 25
         alphabet.Add(ChrW(charValue + ctr).ToString())
      Next
      Return alphabet 
   End Function
End Module
' The example displays the following output:
'       MNOPQRSTUVWXYZ

Concat(Object, Object)

Source:

String.Manipulation.cs

Concatenates the string representations of two specified objects.

public:
 static System::String ^ Concat(System::Object ^ arg0, System::Object ^ arg1);

public static string Concat (object? arg0, object? arg1);

static member Concat : obj * obj -> string

Public Shared Function Concat (arg0 As Object, arg1 As Object) As String

Parameters

arg0

Object

The first object to concatenate.

arg1

Object

The second object to concatenate.

Returns

String

The concatenated string representations of the values of arg0 and arg1.

Examples

The following example demonstrates the Concat method.

using namespace System;

int main()
{
   int i = -123;
   Object^ o = i;
   array<Object^>^objs = { -123, -456, -789};
   Console::WriteLine("Concatenate 1, 2, and 3 objects:");
   Console::WriteLine("1) {0}", String::Concat(o));
   Console::WriteLine("2) {0}", String::Concat(o, o));
   Console::WriteLine("3) {0}", String::Concat(o, o, o));
   
   Console::WriteLine("\nConcatenate 4 objects and a variable length parameter list:" );
   Console::WriteLine("4) {0}", String::Concat(o, o, o, o));
   Console::WriteLine("5) {0}", String::Concat( o, o, o, o, o));
   Console::WriteLine("\nConcatenate a 3-element object array:");
   Console::WriteLine("6) {0}", String::Concat(objs));
}
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//    
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//    
//    Concatenate a 3-element object array:
//    6) -123-456-789

using System;

class stringConcat5 {
    public static void Main() {
    int i = -123;
    Object o = i;
    Object[] objs = new Object[] {-123, -456, -789};

    Console.WriteLine("Concatenate 1, 2, and 3 objects:");
    Console.WriteLine("1) {0}", String.Concat(o));
    Console.WriteLine("2) {0}", String.Concat(o, o));
    Console.WriteLine("3) {0}", String.Concat(o, o, o));

    Console.WriteLine("\nConcatenate 4 objects and a variable length parameter list:");
    Console.WriteLine("4) {0}", String.Concat(o, o, o, o));
    Console.WriteLine("5) {0}", String.Concat(o, o, o, o, o));

    Console.WriteLine("\nConcatenate a 3-element object array:");
    Console.WriteLine("6) {0}", String.Concat(objs));
    }
}
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//
//    Concatenate a 3-element object array:
//    6) -123-456-789

open System

let i = -123
let o: obj = i
let objs: obj[] = [| -123; -456; -789 |]

printfn "Concatenate 1, 2, and 3 objects:"
printfn $"1) {String.Concat o}"
printfn $"2) {String.Concat(o, o)}"
printfn $"3) {String.Concat(o, o, o)}"

printfn "\nConcatenate 4 objects and a variable length parameter list:"
printfn $"4) {String.Concat(o, o, o, o)}"
printfn $"5) {String.Concat(o, o, o, o, o)}"

printfn "\nConcatenate a 3-element object array:"
printfn $"6) {String.Concat objs}" 
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//
//    Concatenate a 3-element object array:
//    6) -123-456-789

Class stringConcat5
   Public Shared Sub Main()
      Dim i As Integer = - 123
      Dim o As [Object] = i
      Dim objs() As [Object] = {-123, -456, -789}
      
      Console.WriteLine("Concatenate 1, 2, and 3 objects:")
      Console.WriteLine("1) {0}", [String].Concat(o))
      Console.WriteLine("2) {0}", [String].Concat(o, o))
      Console.WriteLine("3) {0}", [String].Concat(o, o, o))
      
      Console.WriteLine(vbCrLf & "Concatenate 4 objects and a variable length parameter list:")
      Console.WriteLine("4) {0}", String.Concat(o, o, o, o))
      Console.WriteLine("5) {0}", String.Concat(o, o, o, o, o))
      
      Console.WriteLine(vbCrLf & "Concatenate a 3-element object array:")
      Console.WriteLine("6) {0}", [String].Concat(objs))
   End Sub
End Class
'The example displays the following output:
'    Concatenate 1, 2, and 3 objects:
'    1) -123
'    2) -123-123
'    3) -123-123-123
'    
'    Concatenate 4 objects and a variable length parameter list:
'    4) -123-123-123-123
'    5) -123-123-123-123-123
'         
'    Concatenate a 3-element object array:
'    6) -123-456-789

Remarks

The method concatenates arg0 and arg1 by calling the parameterless ToString method of arg0 and arg1; it does not add any delimiters.

String.Empty is used in place of any null argument.

If either of the arguments is an array reference, the method concatenates a string representing that array, instead of its members (for example, "System.String[]").

See also

• Object
• Join(String, String[])

Concat(String[])

Source:

String.Manipulation.cs

Important

This API is not CLS-compliant.

Concatenates the elements of a specified String array.

public:
 static System::String ^ Concat(... cli::array <System::String ^> ^ values);

public static string Concat (params string?[] values);

static member Concat : string[] -> string

Public Shared Function Concat (ParamArray values As String()) As String

Parameters

values

String[]

An array of string instances.

Returns

String

The concatenated elements of values.

Exceptions

ArgumentNullException

values is null.

OutOfMemoryException

Out of memory.

Examples

The following example demonstrates the use of the Concat method with a String array.

using namespace System;

int main()
{
   
   // Make an array of strings. Note that we have included spaces.
   array<String^>^s = { "hello ", "and ", "welcome ", "to ",
                        "this ", "demo! "};
   
   // Put all the strings together.
   Console::WriteLine( String::Concat(s) );
   
   // Sort the strings, and put them together.
   Array::Sort( s );
   Console::WriteLine( String::Concat(s));
}
// The example displays the following output:
//       hello and welcome to this demo!
//       and demo! hello this to welcome

using System;

public class Example
{
    public static void Main()
    {
        // Make an array of strings. Note that we have included spaces.
        string [] s = { "hello ", "and ", "welcome ", "to ",
                        "this ", "demo! " };

        // Put all the strings together.
        Console.WriteLine(string.Concat(s));

        // Sort the strings, and put them together.
        Array.Sort(s);
        Console.WriteLine(string.Concat(s));
    }
}
// The example displays the following output:
//       hello and welcome to this demo!
//       and demo! hello this to welcome

open System

// Make an array of strings. Note that we have included spaces.
let s = 
    [| "hello "; "and "; "welcome "; "to "
       "this "; "demo! " |]

// Put all the strings together.
printfn $"{String.Concat s}"

// Sort the strings, and put them together.
Array.Sort s
printfn $"{String.Concat s}"
// The example displays the following output:
//       hello and welcome to this demo!
//       and demo! hello this to welcome

Public Class Example
    Public Shared Sub Main()
        ' Make an array of strings. Note that we have included spaces.
        Dim s As String() = { "hello ", "and ", "welcome ", "to ",
                              "this ", "demo! "}

        ' Put all the strings together.
        Console.WriteLine(String.Concat(s))
        
        ' Sort the strings, and put them together.
        Array.Sort(s)
        Console.WriteLine(String.Concat(s))
    End Sub
End Class
' The example displays the following output:
'       hello and welcome to this demo!
'       and demo! hello this to welcome

Remarks

The method concatenates each object in values; it does not add any delimiters.

An Empty string is used in place of any null object in the array.

See also

• Join(String, String[])

Concat(ReadOnlySpan<String>)

Concatenates the elements of a specified span of String.

public:
 static System::String ^ Concat(ReadOnlySpan<System::String ^> values);

public static string Concat (scoped ReadOnlySpan<string?> values);

static member Concat : ReadOnlySpan<string> -> string

Public Shared Function Concat (values As ReadOnlySpan(Of String)) As String

Parameters

values

ReadOnlySpan<String>

A span of String instances.

Returns

String

The concatenated elements of values.

Concat(ReadOnlySpan<Object>)

Concatenates the string representations of the elements in a specified span of objects.

public:
 static System::String ^ Concat(ReadOnlySpan<System::Object ^> args);

public static string Concat (scoped ReadOnlySpan<object?> args);

static member Concat : ReadOnlySpan<obj> -> string

Public Shared Function Concat (args As ReadOnlySpan(Of Object)) As String

Parameters

args

ReadOnlySpan<Object>

A span of objects that contains the elements to concatenate.

Returns

String

The concatenated string representations of the values of the elements in args.

Concat(Object[])

Source:

String.Manipulation.cs

Concatenates the string representations of the elements in a specified Object array.

public:
 static System::String ^ Concat(... cli::array <System::Object ^> ^ args);

public static string Concat (params object?[] args);

static member Concat : obj[] -> string

Public Shared Function Concat (ParamArray args As Object()) As String

Parameters

args

Object[]

An object array that contains the elements to concatenate.

Returns

String

The concatenated string representations of the values of the elements in args.

Exceptions

ArgumentNullException

args is null.

OutOfMemoryException

Out of memory.

Examples

The following example demonstrates the use of the Concat method with an Object array.

using System;

public class ConcatTest {
    public static void Main() {
        // Create a group of objects.
        Test1 t1 = new Test1();
        Test2 t2 = new Test2();
        int i = 16;
        string s = "Demonstration";

        // Place the objects in an array.
        object [] o = { t1, i, t2, s };

        // Concatenate the objects together as a string. To do this,
        // the ToString method of each of the objects is called.
        Console.WriteLine(string.Concat(o));
    }
}

// Create two empty test classes.
class Test1 {
}

class Test2 {
}
// The example displays the following output:
//       Test116Test2Demonstration

open System

// Create two empty test classes.
type Test1() = class end

type Test2() = class end

// Create a group of objects.
let t1 = new Test1()
let t2 = new Test2()
let i = 16
let s = "Demonstration"

// Place the objects in an array.
let o: obj[] = [| t1; i; t2; s |]

// Concatenate the objects together as a string. To do this,
// the ToString method of each of the objects is called.
printfn $"{String.Concat o}"

// The example displays the following output:
//       Test116Test2Demonstration

Public Class ConcatTest
    
    Public Shared Sub Main()
        Dim t1 As New Test1()
        Dim t2 As New Test2()
        Dim i As Integer = 16
        Dim s As String = "Demonstration"
        Dim o As Object() = {t1, i, t2, s}
        
        ' create a group of objects
        
        ' place the objects in an array
        
        ' concatenate the objects together as a string. To do this,
        ' the ToString method in the objects is called
        Console.WriteLine(String.Concat(o))
    End Sub
End Class


' imagine these test classes are full-fledged objects...
Class Test1
End Class

Class Test2
End Class

Remarks

The method concatenates each object in args by calling the parameterless ToString method of that object; it does not add any delimiters.

String.Empty is used in place of any null object in the array.

Notes to Callers

This method is not called by C++ code. The C++ compiler resolves calls to Concat that have four or more object parameters as a call to Concat(Object, Object, Object, Object).

See also

• Object
• Join(String, String[])

Concat(Object)

Source:

String.Manipulation.cs

Creates the string representation of a specified object.

public:
 static System::String ^ Concat(System::Object ^ arg0);

public static string Concat (object? arg0);

static member Concat : obj -> string

Public Shared Function Concat (arg0 As Object) As String

Parameters

arg0

Object

The object to represent, or null.

Returns

String

The string representation of the value of arg0, or Empty if arg0 is null.

Examples

The following example demonstrates the Concat method.

using namespace System;

int main()
{
   int i = -123;
   Object^ o = i;
   array<Object^>^objs = { -123, -456, -789};
   Console::WriteLine("Concatenate 1, 2, and 3 objects:");
   Console::WriteLine("1) {0}", String::Concat(o));
   Console::WriteLine("2) {0}", String::Concat(o, o));
   Console::WriteLine("3) {0}", String::Concat(o, o, o));
   
   Console::WriteLine("\nConcatenate 4 objects and a variable length parameter list:" );
   Console::WriteLine("4) {0}", String::Concat(o, o, o, o));
   Console::WriteLine("5) {0}", String::Concat( o, o, o, o, o));
   Console::WriteLine("\nConcatenate a 3-element object array:");
   Console::WriteLine("6) {0}", String::Concat(objs));
}
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//    
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//    
//    Concatenate a 3-element object array:
//    6) -123-456-789

using System;

class stringConcat5 {
    public static void Main() {
    int i = -123;
    Object o = i;
    Object[] objs = new Object[] {-123, -456, -789};

    Console.WriteLine("Concatenate 1, 2, and 3 objects:");
    Console.WriteLine("1) {0}", String.Concat(o));
    Console.WriteLine("2) {0}", String.Concat(o, o));
    Console.WriteLine("3) {0}", String.Concat(o, o, o));

    Console.WriteLine("\nConcatenate 4 objects and a variable length parameter list:");
    Console.WriteLine("4) {0}", String.Concat(o, o, o, o));
    Console.WriteLine("5) {0}", String.Concat(o, o, o, o, o));

    Console.WriteLine("\nConcatenate a 3-element object array:");
    Console.WriteLine("6) {0}", String.Concat(objs));
    }
}
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//
//    Concatenate a 3-element object array:
//    6) -123-456-789

open System

let i = -123
let o: obj = i
let objs: obj[] = [| -123; -456; -789 |]

printfn "Concatenate 1, 2, and 3 objects:"
printfn $"1) {String.Concat o}"
printfn $"2) {String.Concat(o, o)}"
printfn $"3) {String.Concat(o, o, o)}"

printfn "\nConcatenate 4 objects and a variable length parameter list:"
printfn $"4) {String.Concat(o, o, o, o)}"
printfn $"5) {String.Concat(o, o, o, o, o)}"

printfn "\nConcatenate a 3-element object array:"
printfn $"6) {String.Concat objs}" 
// The example displays the following output:
//    Concatenate 1, 2, and 3 objects:
//    1) -123
//    2) -123-123
//    3) -123-123-123
//
//    Concatenate 4 objects and a variable length parameter list:
//    4) -123-123-123-123
//    5) -123-123-123-123-123
//
//    Concatenate a 3-element object array:
//    6) -123-456-789

Class stringConcat5
   Public Shared Sub Main()
      Dim i As Integer = - 123
      Dim o As [Object] = i
      Dim objs() As [Object] = {-123, -456, -789}
      
      Console.WriteLine("Concatenate 1, 2, and 3 objects:")
      Console.WriteLine("1) {0}", [String].Concat(o))
      Console.WriteLine("2) {0}", [String].Concat(o, o))
      Console.WriteLine("3) {0}", [String].Concat(o, o, o))
      
      Console.WriteLine(vbCrLf & "Concatenate 4 objects and a variable length parameter list:")
      Console.WriteLine("4) {0}", String.Concat(o, o, o, o))
      Console.WriteLine("5) {0}", String.Concat(o, o, o, o, o))
      
      Console.WriteLine(vbCrLf & "Concatenate a 3-element object array:")
      Console.WriteLine("6) {0}", [String].Concat(objs))
   End Sub
End Class
'The example displays the following output:
'    Concatenate 1, 2, and 3 objects:
'    1) -123
'    2) -123-123
'    3) -123-123-123
'    
'    Concatenate 4 objects and a variable length parameter list:
'    4) -123-123-123-123
'    5) -123-123-123-123-123
'         
'    Concatenate a 3-element object array:
'    6) -123-456-789

Remarks

The Concat(Object) method represents arg0 as a string by calling its parameterless ToString method.

See also

• Object
• Join(String, String[])

Concat(ReadOnlySpan<Char>, ReadOnlySpan<Char>)

Source:

String.Manipulation.cs

Concatenates the string representations of two specified read-only character spans.

public:
 static System::String ^ Concat(ReadOnlySpan<char> str0, ReadOnlySpan<char> str1);

public static string Concat (ReadOnlySpan<char> str0, ReadOnlySpan<char> str1);

static member Concat : ReadOnlySpan<char> * ReadOnlySpan<char> -> string

Public Shared Function Concat (str0 As ReadOnlySpan(Of Char), str1 As ReadOnlySpan(Of Char)) As String

Parameters

str0

ReadOnlySpan<Char>

The first read-only character span to concatenate.

str1

ReadOnlySpan<Char>

The second read-only character span to concatenate.

Returns

String

The concatenated string representations of the values of str0 and str1.

Concat<T>(IEnumerable<T>)

Source:

String.Manipulation.cs

Concatenates the members of an IEnumerable<T> implementation.

public:
generic <typename T>
 static System::String ^ Concat(System::Collections::Generic::IEnumerable<T> ^ values);

public static string Concat<T> (System.Collections.Generic.IEnumerable<T> values);

static member Concat : seq<'T> -> string

Public Shared Function Concat(Of T) (values As IEnumerable(Of T)) As String

Type Parameters

T

The type of the members of values.

Parameters

values

IEnumerable<T>

A collection object that implements the IEnumerable<T> interface.

Returns

String

The concatenated members in values.

Exceptions

ArgumentNullException

values is null.

Examples

The following example defines a very simple Animal class that contains the name of an animal and the order to which it belongs. It then defines a List<T> object to contain a number of Animal objects. The Enumerable.Where extension method is called to extract the Animal objects whose Order property equals "Rodent". The result is passed to the Concat<T>(IEnumerable<T>) method and displayed to the console.

using System;
using System.Collections.Generic;
using System.Linq;

public class Animal
{
   public string Kind;
   public string Order;
   
   public Animal(string kind, string order)
   {
      this.Kind = kind;
      this.Order = order;
   }
   
   public override string ToString()
   {
      return this.Kind;
   }
}

public class Example
{
   public static void Main()
   {
      List<Animal> animals = new List<Animal>();
      animals.Add(new Animal("Squirrel", "Rodent"));
      animals.Add(new Animal("Gray Wolf", "Carnivora"));
      animals.Add(new Animal("Capybara", "Rodent"));
      string output = String.Concat(animals.Where( animal => 
                      (animal.Order == "Rodent")));
      Console.WriteLine(output);  
   }
}
// The example displays the following output:
//      SquirrelCapybara

// This example uses the F# Seq.filter function instead of Linq.
open System

type Animal =
  { Kind: string
    Order: string }
    override this.ToString() =
       this.Kind

let animals = ResizeArray()
animals.Add { Kind = "Squirrel"; Order = "Rodent" }
animals.Add { Kind = "Gray Wolf"; Order = "Carnivora" }
animals.Add { Kind = "Capybara"; Order = "Rodent" }

Seq.filter (fun animal -> animal.Order = "Rodent")
|> String.Concat
|> printfn "%s"
// The example displays the following output:
//      SquirrelCapybara

Imports System.Collections.Generic

Public Class Animal
   Public Kind As String
   Public Order As String
   
   Public Sub New(kind As String, order As String)
      Me.Kind = kind
      Me.Order = order
   End Sub
   
   Public Overrides Function ToString() As String
      Return Me.Kind
   End Function
End Class

Module Example
   Public Sub Main()
      Dim animals As New List(Of Animal)
      animals.Add(New Animal("Squirrel", "Rodent"))
      animals.Add(New Animal("Gray Wolf", "Carnivora"))
      animals.Add(New Animal("Capybara", "Rodent")) 
      Dim output As String = String.Concat(animals.Where(Function(animal) _
                                           animal.Order = "Rodent"))
      Console.WriteLine(output)                                           
   End Sub
End Module
' The example displays the following output:
'      SquirrelCapybara

Remarks

The method concatenates each object in values; it does not add any delimiters.

An Empty string is used in place of any null argument.

Concat<T>(IEnumerable<T>) is a convenience method that lets you concatenate each element in an IEnumerable<T> collection without first converting the elements to strings. It is particularly useful with Language-Integrated Query (LINQ) query expressions, as the example illustrates. The string representation of each object in the IEnumerable<T> collection is derived by calling that object's ToString method.