public class Program

{

    public class A

    {

          //base class method, created with keyword 'virtual'

      public virtual  void Display()

      {

         System.Console.WriteLine("A::Display");

      }

    }

​

    public class B :A

    {

           // dervied class methodm with new definition using override

       public override void Display()

      {

         System.Console.WriteLine("B::Display");

      }

    }

​

      public static void Main()

      {

         A a;

         a = new A();

         a.Display();    

​

         a = new B();

         a.Display();    

      }

​

}