C# | String.ToUpperInvariant Method

Last Updated : 11 Jul, 2025

String.ToUpperInvariant Method is used to get a copy of this String object converted to uppercase using the casing rules of the invariant culture. Here "invariant culture" represents a culture that is culture-insensitive.
Syntax:

public string ToUpperInvariant ();

Return Value: The return type of this method is System.String. This method will return a string which is the uppercase equivalent of the current string.
Below given are some examples to understand the implementation in a better way:
Example 1:

CSharp

// C# program to illustrate
// ToUpperInvariant() method
using System;

public class GFG {

    // Main method
    static public void Main()
    {

        // variables
        string strA = "WelCome tO GeeKSfOrGeeKs";
        string strB;

        // Convert strA into lowercase
        // using ToLowerInvariant() method
        strB = strA.ToUpperInvariant();

        // Display string before ToUpperInvariant() method
        Console.WriteLine("String before ToUpperInvariant:");
        Console.WriteLine(strA);
        Console.WriteLine();

        // Display string after ToUpperInvariant() method
        Console.WriteLine("String after ToUpperInvariant:");
        Console.WriteLine(strB);
    }
}

Output:

String before ToUpperInvariant:
WelCome tO GeeKSfOrGeeKs

String after ToUpperInvariant:
WELCOME TO GEEKSFORGEEKS

Example 2:

CSharp

// C# program to illustrate 
// ToUpperInvariant() Method
using System;

public class GFG {

    // Main method
    static public void Main()
    {

        // Calling function
        Convert("GEeks");
        Convert("geeks");
        Convert("GEEKS");
    }

    static void Convert(String value)
    {

        // Display  strings
        Console.WriteLine("string 1:  {0}", value);

        // Convert string into Uppercase
        // using ToUpperInvariant() method
        value = value.ToUpperInvariant();

        // Display the Lowercase strings
        Console.WriteLine("string 2:  {0}", value);
    }
}

Output:

string 1:  GEeks
string 2:  GEEKS
string 1:  geeks
string 2:  GEEKS
string 1:  GEEKS
string 2:  GEEKS

Note:

The invariant culture represents a culture that is culture-insensitive. It is associated with the English language but not with a specific country or region.
ToUpperInvariant() 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 uppercase.
This method can't be overloaded if you try to overload this method, it will give you compile time error.

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