using System;

using System.Text;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        Henk henk = null;

        Console.WriteLine(henk.Henkie());

    }

}

​

​

    public class Henk 

    {

    }

    public static class Henker 

    {

        public static string Henkie(this Henk henk) 

        {

            return "henkie";

        }

    }