using System;

public class Program

{

    public static void Main()

    {

        Base objBase = new Base();

        objBase.Message(); // I amd Base

        Derived objDerived = new Derived();

        objDerived.Message(); // I am Derived

        // Now, set the reference of derived class to base class.

        objBase = new Derived();

        objBase.Message(); // I am Base

    }

}

​

​

public class Base

{

    public virtual void Message()

    {

        Console.WriteLine("I am Base");

    }

}

​

public class Derived : Base

{

    public override void  Message()

    {

        Console.WriteLine("I am Derived");

    }

}