In C#, ToLower() is a string method. It converts every character to lowercase (if there is a lowercase character). If a character does not have a lowercase equivalent, it remains unchanged. For example, special symbols remain unchanged. This method can be overloaded by passing the different type of arguments to it.

• String.ToLower() Method
• String.ToLower(CultureInfo) Method

String.ToLower() Method

This method is used to return a copy of the current string converted to lowercase.

Syntax:

public string ToLower ();

Return Type: It return the string value, which is the lowercase equivalent of the string of type System.String.

Example:

Input : str  = "GeeksForGeeks"
        str.ToLower()
Output: geeksforgeeks

Input : str  = "This is C# Program xsdD_$#%"
        str.ToLower()
Output: this is c# program xsdd_$#%

Below Programs illustrate the use ToLower() Method:

• Example 1:
  
  

  
  
  

  // C# program to desmonstrate the  // use of ToLower() method  using System;    class Program {        // Main Method     public static void Main()     {            // original string         string str1 = "GeeksForGeeks";            // string converted to lower case         string lowerstr1 = str1.ToLower();            Console.WriteLine(lowerstr1);     } }

  Output:

  geeksforgeeks
  

• Example 2:
  
  

  
  
  

  // C# program to desmonstrate the  // use of ToLower() method  using System;    class Program {        // Main Method     public static void Main()     {            // original string containing the special         // symbol. Here special symbol will remain          // unchange         string str2 = "This is C# Program xsdD_$#%";            // string converted to lower case         string lowerstr2 = str2.ToLower();            Console.WriteLine(lowerstr2);     } }

  Output:

  this is c# program xsdd_$#%
  

String.ToLower(CultureInfo) Method

This method is used to return a copy of the current string converted to lowercase, using the casing rules of the specified culture.

Syntax:

public string ToLower (System.Globalization.CultureInfo culture);

Parameter:

culture: It is the required object which supplies culture-specific casing rules.

Return Type: This method returns the lowercase equivalent of the current string of type System.String.

Exception: This method can give ArgumentNullException if the value of culture is null.

Example:

Output:

this is c# program xsdd_$#%

Note: These methods will not modify the value of the current instance. Instead, returns a new string in which all characters in the current instance will convert to lowercase.

Reference: https://docs.microsoft.com/en-us/dotnet/api/system.string.tolower?view=netframework-4.7.2

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