using System;

    namespace PolimorfismoApplication{

    abstract class Forma{

        public abstract int area();

    }

        class Rectangulo:Forma{

            private int largo;

            private int ancho;

            public Rectangulo(int a=0,int b=0){

            largo = a;

            ancho = b;

            }

            public override int area(){

            Console.WriteLine("Rectangulo clase area:");

            return(ancho*largo);

            }

        }

        class Rectangulo Tester{

        static void Main(string[] args){

        Rectangulo r= new Rectangulo(10,7);

            double a= r.area();

            Console.WriteLine("Area:{0}",a);

            Console.ReadKey();

            }

        }

    }

​

​