C# | ToLower() Method - GeeksforGeeks

31 Jan, 2019
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
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

// 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_$#%";          // string converted to lower case        string lowerstr2 = str2.ToLower();          Console.WriteLine(lowerstr2);    }}Output:this is c# program xsdd_$#%

// 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_$#%";          // string converted to lower case        string lowerstr2 = str2.ToLower();          Console.WriteLine(lowerstr2);    }}
Output:
this is c# program xsdd_$#%

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:
// C# program to desmonstrate the // use of ToLower(CultureInfo) method using System;using System.Globalization;  class Program {      // Main Method    public static void Main()    {        // original string        string str2 = "THIS IS C# PROGRAM XSDD_$#%";          // string converted to lowercase by        // using English-United States culture        string lowerstr2 = str2.ToLower(new CultureInfo("en-US", false));          Console.WriteLine(lowerstr2);    }}
Output:
this is c# program xsdd_$#%

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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