装饰（Decorator）模式

装饰模式应当在什么情况下使用

引用：http://www.cnblogs.com/singlepine/archive/2005/10/30/265023.html

在以下情况下应当使用装饰模式：

1. 需要扩展一个类的功能，或给一个类增加附加责任。
2. 需要动态地给一个对象增加功能，这些功能可以再动态地撤销。
3. 需要增加由一些基本功能的排列组合而产生的非常大量的功能，从而使继承关系变得不现实。
   以下是程杰的大话设计模式当中的例子，比较容易理解：

   using System;
   using System.Collections.Generic;
   using System.Text;

   namespace 装饰模式
   {
       class Program
       {
           static void Main(string[] args)
           {
               Person xc = new Person("小菜");

               Console.WriteLine("\n第一种装扮：");

               Sneakers pqx = new Sneakers();
               BigTrouser kk = new BigTrouser();
               TShirts dtx = new TShirts();

               pqx.Decorate(xc);
               kk.Decorate(pqx);
               dtx.Decorate(kk);
               dtx.Show();

               Console.WriteLine("\n第二种装扮：");

               LeatherShoes px = new LeatherShoes();
               Tie ld = new Tie();
               Suit xz = new Suit();

               px.Decorate(xc);
               ld.Decorate(px);
               xz.Decorate(ld);
               xz.Show();

               Console.WriteLine("\n第三种装扮：");
               Sneakers pqx2 = new Sneakers();
               LeatherShoes px2 = new LeatherShoes();
               BigTrouser kk2 = new BigTrouser();
               Tie ld2 = new Tie();

               pqx2.Decorate(xc);
               px2.Decorate(pqx);
               kk2.Decorate(px2);
               ld2.Decorate(kk2);

               ld2.Show();

               Console.Read();
           }
       }

       class Person
       {
           public Person()
           { }

           private string name;
           public Person(string name)
           {
               this.name = name;
           }

           public virtual void Show()
           {
               Console.WriteLine("装扮的{0}", name);
           }
       }

       class Finery : Person
       {
           protected Person component;

           //打扮
           public void Decorate(Person component)
           {
               this.component = component;
           }

           public override void Show()
           {
               if (component != null)
               {
                   component.Show();
               }
           }
       }

   
       class TShirts : Finery
       {
           public override void Show()
           {
               Console.Write("大T恤 ");
               base.Show();
           }
       }

       class BigTrouser : Finery
       {
           public override void Show()
           {
               Console.Write("垮裤 ");
               base.Show();
           }
       }

       class Sneakers : Finery
       {
           public override void Show()
           {
               Console.Write("破球鞋 ");
               base.Show();
           }
       }

       class Suit : Finery
       {
           public override void Show()
           {
               Console.Write("西装 ");
               base.Show();
           }
       }

       class Tie : Finery
       {
           public override void Show()
           {
               Console.Write("领带 ");
               base.Show();
           }
       }

       class LeatherShoes : Finery
       {
           public override void Show()
           {
               Console.Write("皮鞋 ");
               base.Show();
           }
       }
   }