Multi-Dispatch in C#

    interface IA { }

    interface IB { }

    class CA1 : IA {}

    class CA2 : IA {}

    class CA11 : CA1 {}

    class CB1 : IB {}

    class CB2 : IB {}

    class MD

    {

        public enum X { X } ;

        public static void Foo(IA a, IB b, X dispatch = X.X) { Foo((dynamic)a, (dynamic)b); }

        static void Foo(IA a, IB b) { Console.WriteLine("IA IB"); }

        static void Foo(CA1 a, CB1 b) { Console.WriteLine("CA1 CB1"); }

        static void Foo(CA2 a, CB1 b) { Console.WriteLine("CA2 CB1"); }

        static void Foo(CA1 a, CB2 b) { Console.WriteLine("CA1 CB2"); }

        static void Foo(CA2 a, CB2 b) { Console.WriteLine("CA2 CB2"); }

        static void Foo(CA11 a, CB2 b) { Console.WriteLine("CA11 CB2"); }

    }

    class Program

    {

        static void Main(string[] args)

        {

            var a1 = new CA1();

            var a11 = new CA11();

            var a2 = new CA2();

            var b1 = new CB1();

            var b2 = new CB2();

            MD.Foo(a1, b1);

            MD.Foo(a2, b1);

            MD.Foo(a1, b2);

            MD.Foo(a2, b2);

            MD.Foo(a11, b1);

            MD.Foo(a11, b2);

        }

    }