using System;

​

namespace pp_other

{

    public class Program

    {

        public static void Main(string[] args)

        {

            var c = new C();

            c.Method();

​

        }

    }

​

    public class A

    {

        char body = '1';

    }

​

    public class B : A

    {

        char body = '2';

    }

​

    public class C : B

    {

        char body = '3';

    }

​

    internal static class extender

    {

        internal static void Method(this A a)

        {

            Console.Write("A");

        }

​

        internal static void Method(this B b)

        {

            Console.Write("B");

        }

​

        internal static void Method(this C c)

        {

            Console.Write("A");

        }

​

    }

}

​