using System;

public class Program

{

    class Base

{

    public virtual void Foo(int x)

    {

        Console.WriteLine ("Base.Foo(int)");

    }

}

​

class Derived : Base

{

    public override void Foo(int x)

    {

        Console.WriteLine ("Derived.Foo(int)");

    }

   /* public void Foo(object o)

    {

        Console.WriteLine ("Derived.Foo(object)");

    }*/

}

    public static void Main()

    {

        {

        Derived d = new Derived();

        int i = 10;

        d.Foo(i);

    }

    }

}