using System;

public class Program

{

    public static void Main()

    {

        // This calls method String.ToUpper()

        var myString = "Hello World!".ToUpper();

        Console.WriteLine(myString);

​

        // This calls the extension method StringExtensions.Shorten()

        var newString = myString.Shorten(5); 

        Console.WriteLine(newString);

        // It is worth noting that the above call is purely syntactic sugar

        // and this assignment is functionally equivalent

        var newString2 = StringExtensions.Shorten(myString, 5);

        Console.WriteLine(newString2);

    }

}

​

static class StringExtensions

{

    public static string Shorten(this string text, int length) 

    {

        // Truncate a string to n characters

        return text.Substring(0,length);

    }

}