using System;

public class Program

{

    public static void Main()

    {

        var button = new Button();

        var view = button as View;

        var helper = view as IHelper;

        Console.WriteLine("Hello World = " + helper.Get());

    }

}

​

class Button : View, IHelper

{

    string IHelper.Get() { return "button"; }

}

​

class View : IHelper

{

    string IHelper.Get() { return "view"; }

}

​

interface IHelper

{

    string Get();

}

​