using System; using System.Collections.Generic; public class Shape { // A few example members public int X { get; private set; } public int Y { get; private set; } public int Height { get; set; } public int Width { get; set; } // Virtual method public virtual void Draw() { Console.WriteLine("Performing base class drawing tasks"); } } class Circle : Shape { public override void Draw() { // Code to draw a circle... Console.WriteLine("Drawing a circle"); base.Draw(); } } class Rectangle : Shape { public override void Draw() { // Code to draw a rectangle... Console.WriteLine("Drawing a rectangle"); base.Draw(); } } class Triangle : Shape { public override void Draw() { // Code to draw a triangle... Console.WriteLine("Drawing a triangle"); base.Draw(); } } class Program { static void Main(string[] args) { // Polymorphism at work #1: a Rectangle, Triangle and Circle // can all be used whereever a Shape is expected. No cast is // required because an implicit conversion exists from a derived // class to its base class. var shapes = new List{ new Rectangle(), new Triangle(), new Circle() }; // Polymorphism at work #2: the virtual method Draw is // invoked on each of the derived classes, not the base class. foreach (var shape in shapes) { shape.Draw(); } // Keep the console open in debug mode. Console.WriteLine("Press any key to exit."); Console.ReadKey(); } } /* Output: Drawing a rectangle Performing base class drawing tasks Drawing a triangle Performing base class drawing tasks Drawing a circle Performing base class drawing tasks */