using System;

using System.IO;

class C {

   public void m1(int n) {

      Console.WriteLine("m1({0})",n);

   } 

}

​

static class MyExtension {

   public static void m2(this C obj, int n) {

      Console.WriteLine("m2({0})",n);

   }

}

​

public class TesteExt {

   public static void Main() {

      C o = new C();

      o.m1(3);

      o.m2(4);

   }

}