C#多態機制

 1 using System; 2  3 public class DrawingObject 4 { 5     public virtual void Draw() 6     { 7         Console.WriteLine("I'm just a generic drawing object."); 8     } 9 }10 11 using System;12 13 public class Line : DrawingObject14 {15     public override void Draw()16     {17         Console.WriteLine("I'm a Line.");18     }19 }20 21 public class Circle : DrawingObject22 {23     public override void Draw()24     {25         Console.WriteLine("I'm a Circle.");26     }27 }28 29 public class Square : DrawingObject30 {31     public override void Draw()32     {33         Console.WriteLine("I'm a Square.");34     }35 }36 37 using System;38 39 public class DrawDemo40 {41     public static int Main( )42     {43         DrawingObject[] dObj = new DrawingObject[4];44 45         dObj[0] = new Line();46         dObj[1] = new Circle();47         dObj[2] = new Square();48         dObj[3] = new DrawingObject();49 50         foreach (DrawingObject drawObj in dObj)51         {52             drawObj.Draw();53         }54 55         return 0;56     }57 }58 59 Output:60 61 I'm a Line.62 I'm a Circle.63 I'm a Square.64 I'm just a generic drawing object.

與C++相比，C#是一門明確的語言。子類重載了父類的函數要用new，重載了虛函數要用override，還能直接用base指代父類。