using System;

public class Program

{

    public static void Main()

    {

        var test = "somestring";

        Console.WriteLine(test.MyUpperCase());

        Console.WriteLine(test.AddGarbage());

    }

}

​

public static class ExtensionMethods{

    public static string MyUpperCase(this string str)

    {

        return str.ToUpper();

    }

    public static string AddGarbage(this string garbage){

        return garbage + "more garbage";

    }

}