using System;

​

class FarmAnimal 

{

    public virtual void M() { Console.WriteLine("M on FarmAnimal"); }

}

​

class Chicken : FarmAnimal 

{

    public override void M() { Console.WriteLine("M on Chicken"); }

    public void CM() { Console.WriteLine("Chicken only action"); }

}

​

public class Program

{

    public static void Main()

    {

        Chicken c = new Chicken();

        FarmAnimal f = (FarmAnimal) c;

        Object o = (Object) c;

        c.M();

        f.M();

        // f.CM(); Cannot use CM even though f has a chicken object in it.

    }

}