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String.ToLower Method

Definition

Returns a copy of this string converted to lowercase.

Overloads

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.

ToLower()

Source:
String.Manipulation.cs
Source:
String.Manipulation.cs
Source:
String.Manipulation.cs

Returns a copy of this string converted to lowercase.

C#
public string ToLower();

Returns

A string in lowercase.

Examples

The following example converts several mixed case strings to lowercase.

C#
using System;

public class ToLowerTest {
    public static void Main() {

        string [] info = {"Name", "Title", "Age", "Location", "Gender"};

        Console.WriteLine("The initial values in the array are:");
        foreach (string s in info)
            Console.WriteLine(s);

        Console.WriteLine("{0}The lowercase of these values is:", Environment.NewLine);

        foreach (string s in info)
            Console.WriteLine(s.ToLower());

        Console.WriteLine("{0}The uppercase of these values is:", Environment.NewLine);

        foreach (string s in info)
            Console.WriteLine(s.ToUpper());
    }
}
// The example displays the following output:
//       The initial values in the array are:
//       Name
//       Title
//       Age
//       Location
//       Gender
//
//       The lowercase of these values is:
//       name
//       title
//       age
//       location
//       gender
//
//       The uppercase of these values is:
//       NAME
//       TITLE
//       AGE
//       LOCATION
//       GENDER

Remarks

This method takes into account the casing rules of the current culture.

Note

This method does not modify the value of the current instance. Instead, it returns a new string in which all characters in the current instance are converted to lowercase.

The casing operation that results from calling the ToLower() method takes the casing conventions of the current culture into account. If you need the lowercase or uppercase version of an operating system identifier, such as a file name, named pipe, or registry key, use the ToLowerInvariant or ToUpperInvariant methods. This produces the same result in every culture (unlike the ToLower() method) and performs more efficiently.

Notes to Callers

As explained in Best Practices for Using Strings, we recommend that you avoid calling string casing methods that substitute default values and instead call methods that require parameters to be explicitly specified. To convert a character to lowercase by using the casing conventions of the current culture, signal your intention explicitly by calling the ToLower(CultureInfo) method overload with a value of CurrentCulture for its culture parameter. If you don't need linguistic-aware comparison, consider using Ordinal.

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 2.0, 2.1
UWP 10.0

ToLower(CultureInfo)

Source:
String.Manipulation.cs
Source:
String.Manipulation.cs
Source:
String.Manipulation.cs

Returns a copy of this string converted to lowercase, using the casing rules of the specified culture.

C#
public string ToLower(System.Globalization.CultureInfo? culture);
C#
public string ToLower(System.Globalization.CultureInfo culture);

Parameters

culture
CultureInfo

An object that supplies culture-specific casing rules. If culture is null, the current culture is used.

Returns

The lowercase equivalent of the current string.

Examples

The following example converts two strings of uppercase characters to lowercase characters using the English-United States and Turkish-Turkey cultures, then compares the lowercase strings. The uppercase strings are identical except that for each occurrence of the Unicode LATIN CAPITAL LETTER I in one string, the other string contains LATIN CAPITAL LETTER I WITH DOT ABOVE.

C#
// Sample for String.ToLower(CultureInfo)

using System;
using System.Globalization;

class Sample
{
    public static void Main()
    {
    String str1 = "INDIGO";
    // str2 = str1, except each 'I' is '\u0130' (Unicode LATIN CAPITAL I WITH DOT ABOVE).
    String str2 = new String(new Char[] {'\u0130', 'N', 'D', '\u0130', 'G', 'O'});
    String str3, str4;

    Console.WriteLine();
    Console.WriteLine("str1 = '{0}'", str1);

    Console.WriteLine();
    Console.WriteLine("str1 is {0} to str2.",
         ((0 == String.CompareOrdinal(str1, str2)) ? "equal" : "not equal"));
    CodePoints("str1", str1);
    CodePoints("str2", str2);

    Console.WriteLine();
    // str3 is a lower case copy of str2, using English-United States culture.
    Console.WriteLine("str3 = Lower case copy of str2 using English-United States culture.");
    str3 = str2.ToLower(new CultureInfo("en-US", false));

    // str4 is a lower case copy of str2, using Turkish-Turkey culture.
    Console.WriteLine("str4 = Lower case copy of str2 using Turkish-Turkey culture.");
    str4 = str2.ToLower(new CultureInfo("tr-TR", false));

    // Compare the code points in str3 and str4.
    Console.WriteLine();
    Console.WriteLine("str3 is {0} to str4.",
         ((0 == String.CompareOrdinal(str3, str4)) ? "equal" : "not equal"));
    CodePoints("str3", str3);
    CodePoints("str4", str4);
    }

    public static void CodePoints(String title, String s)
    {
    Console.Write("{0}The code points in {1} are: {0}", Environment.NewLine, title);
    foreach (ushort u in s)
      Console.Write("{0:x4} ", u);
    Console.WriteLine();
    }
}
/*
This example produces the following results:

str1 = 'INDIGO'

str1 is not equal to str2.

The code points in str1 are:
0049 004e 0044 0049 0047 004f

The code points in str2 are:
0130 004e 0044 0130 0047 004f

str3 = Lower case copy of str2 using English-United States culture.
str4 = Lower case copy of str2 using Turkish-Turkey culture.

str3 is equal to str4.

The code points in str3 are:
0069 006e 0064 0069 0067 006f

The code points in str4 are:
0069 006e 0064 0069 0067 006f
*/

Remarks

The casing rules of the culture specified by the culture parameter determine the way the case of the string is changed.

Note

This method does not modify the value of the current instance. Instead, it returns a new string in which all characters in the current instance are converted to lowercase.

If you pass the ToLower(CultureInfo) method a CultureInfo object other than CultureInfo.InvariantCulture, the casing operation will take culture-specific rules into account. If you need the lowercase or uppercase version of an operating system identifier, such as a file name, named pipe, or registry key, use the ToLowerInvariant or ToUpperInvariant method. This produces the same result in every culture and performs more efficiently.

See also

Applies to

.NET 9 and other versions
Product Versions
.NET Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9
.NET Framework 1.1, 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1
.NET Standard 2.0, 2.1