using System;

public class Program

{

    public static void Main()

    {

        var g = new Goo();

        g.Call();

        Console.WriteLine("World");

    }

}

​

public abstract class Foo

{

    private void AddFoo()

    { Console.WriteLine("Hello"); }

}

​

public class Goo : Foo

{

    public void Call(){AddFoo();}

    public void AddFoo()

    { Console.WriteLine("Hello"); }

}