C# String.ToUpper() – Examples

String.ToUpper() method is used to get a copy of the given string converted to uppercase.

This method does not modify the original string, but returns a new string in which all characters in the given string are converted to uppercase.

In this tutorial, we will learn about the syntax of C# String.ToUpper() and C# String.ToUpper() methods, and learn how to use these method with the help of examples.

ToUpper()

String.ToUpper() returns a copy of this string converted to uppercase.

Syntax

The syntax of ToUpper() method is

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String.ToUpper()

Return Value

This method returns String value.

Example 1 – ToUpper()

In this example, we will take a string with some upper-case and some lower-case alphabets, say "Hello World". To get uppercase of this string we will call ToUpper() method on this string. A string with all the upper case characters for the given string should be returned by ToUpper() method.

C# Program

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using System;
 
class Example {
    static void Main(string[] args) {
        String str = "Hello World";
        String result = str.ToUpper();
        Console.WriteLine($"Original String is  : {str}");
        Console.WriteLine($"Result of ToUpper() : {result}");
    }
}

Output

Original String is  : Hello World
Result of ToUpper() : HELLO WORLD

Example 2 – ToUpper() – All Lowercase Characters

In this example, we will take a string with all lowercase alphabets, say abcdef. To get uppercase of this string we will call ToUpper() method on this string. A string with all the uppercase characters for the given string should be returned.

C# Program

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using System;
 
class Example {
    static void Main(string[] args) {
        String str = "abcdef";
        String result = str.ToUpper();
        Console.WriteLine($"Original String is  : {str}");
        Console.WriteLine($"Result of ToUpper() : {result}");
    }
}

Output

Original String is  : abcdef
Result of ToUpper() : ABCDEF

Example 3 – ToUpper() – Null String

In this example, we will take a null string and call ToUpper() method on this null string. ToUpper() should throw System.NullReferenceException.

C# Program

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using System;
 
class Example {
    static void Main(string[] args) {
        String str = null;
        String result = str.ToUpper();
        Console.WriteLine($"Original String is  : {str}");
        Console.WriteLine($"Result of ToUpper() : {result}");
    }
}

Output

Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at Example.Main(String[] args) in D:\workspace\csharp\HelloWorld\Program.cs:line 6

ToUpper(CultureInfo)

String.ToUpper() returns a copy of this string converted to uppercase, using the casing rules of the specified culture.

Syntax

The syntax of ToUpper(CultureInfo) method is

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String.ToUpper(CultureInfo)

Return Value

This method returns String value.

Example 4 – ToUpper(culture)

In this example, we will take a Turkish character in the string. This character is lower case a with double dot on top of it. We will convert this string into upper case, with culture information provided as argument to ToLower() method.

C# Program

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using System;
using System.Globalization;
 
class Example {
    static void Main(string[] args) {
        String str = new String(new Char[] {'\u00E4'});
        String result = str.ToUpper(new CultureInfo("tr-TR", false));
        Console.WriteLine($"Original String is  : {str}");
        Console.WriteLine($"Result of ToUpper() : {result}");
    }
}

Output

Original String is  : ä
Result of ToUpper() : Ä

Conclusion

In this C# Tutorial, we have learnt the syntax of C# String.ToUpper() method, and also learnt how to use this method with the help of C# example programs.