public class Program

{

    public static void Main(string[] args)

    {

        C c = new C();

        A a = new A();

        a = c;

        a.Show();

        c.Show();

        Console.ReadLine();

    }

}

public class A

{

    public virtual void Show()

    {

        Console.WriteLine("A.Show()");

    }     

}

​

public class B : A

{

    public override void Show()

    {

        Console.WriteLine("B.Show()");

    }

}

public class C : B

{

    public new void Show()

    {

        Console.WriteLine("C.Show()");

    }

}

​