using System;

namespace TestSealedClasses 

{

    public class Base

    {

        public virtual void Show()

        {                      

            Console.WriteLine("This is Base Class.");

        }

    }

​

    public class Derived : Base

    {

        public sealed override void Show()

        {

            Console.WriteLine("This is Derived Class.");

        }

    }

    public class NextDerived : Derived

    {

        /* 

        // overriding Show() is not allowed anymore

        public override void Show()

        {

            Console.WriteLine("This is Derived Class.");

        }

        */

    }

    public class Program

    {

        public static void Main(string[] args)

        {

            Base objBaseReference = new Derived();

            objBaseReference.Show();// Output ---------> This is Base Class.

        }

    }

}