using System;

public class A

{

    public virtual void X() 

    {

        Console.WriteLine("A::X()");

    }

    public virtual void Y()

    {

        Console.WriteLine("A::Y()\n");

    }

}

public class B:A

{

    sealed public override void X()

    {

        Console.WriteLine("B::X()");

    }

    public override void Y()

    {

        Console.WriteLine("B::Y()\n");

    }

}

public class C:B

{

    //sealed public virtual void X()

    //{

    //  Console.WriteLine("B::X()");

    //}

    public override void Y()

    {

        Console.WriteLine("C::Y()");

    }

}

public class SealedClassAndMethodTest

{

    public static void Main(string[] args)

    {

        A a= new A();

        a.X();

        a.Y();

        B b= new B();

        b.X();

        b.Y();

        C c= new C();

        c.X();

        c.Y();

    }

}

​