Mega Code Archive
0137 Polymorphism
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Polymorphism means:
Derived class objects can be used whereever a base class object is expected.
The virtual method is invoked on each of the derived classes, not the base class.
using System;
public class Shape
{
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)
{
// Rectangle, Triangle and Circle can
// all be used whereever a Shape is expected.
System.Collections.Generic.List<Shape> shapes =
new System.Collections.Generic.List<Shape>();
shapes.Add(new Rectangle());
shapes.Add(new Triangle());
shapes.Add(new Circle());
// Virtual method Draw is invoked on each of the derived classes, not the base class.
foreach (Shape s in shapes)
{
s.Draw();
}
}
}
The 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
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