using System;

​

namespace Fiddle

{

    public interface IPrintNum {

        void Print(int x);

    }

    public static class IPrintNumExtensions {

        public static void Print(this IPrintNum printer, int x) {

            Console.WriteLine("Running extension method...");

            printer.Print(x);

        }

    }

    public class Printer : IPrintNum {

        public void Print(int x) {

            Console.WriteLine("Running implemented method...");

            Console.WriteLine(x);

        }

    }

    public class Program

    {

        public static void Main()

        {

            IPrintNum p = new Printer();

            p.Print(10);

        }

    }

}