using System;

​

​

class Test

{

   public void Hello(){

       Console.WriteLine("From Test");

   }

}

static class TestExtensions

{

    public static void Hello( this Test test ){

        Console.WriteLine("From extension method");

    }

}

public class Program

{

    public static void Main()

    {

        Test t = new Test();

        t.Hello();

    }

}