我喜欢户外，然后常常去逛户外装备的店子，一般买了自行车等大件，再买登山包，登山鞋等配件就会有优惠。比如买了辆Giant的车，然后买个bag就有优惠，本案例将配件作为装饰者，简单的实现装饰者模式，对于继承，多态掌握的还是很迷惑。有错误还请各位看官帮忙指出，仪器共同进步！

首先定义一个超类Buybike

 public abstract class Buybike{protected string description="To Get a Bike";public virtual string getDescription(){return description;}public abstract string Cost();}

超类下面定义一个装饰者超类OtherDecorator（所有装饰者【案例中配件】的父类）

public abstract class OtherDecorator:Buybike{//只是为了将装饰者全部置于其下，无具体实现方法}

下面是两个被装饰的类Giant Merida（捷安特，美利达）

class Merida:Buybike{public Merida(){description = "Merida";}public override string Cost(){return "2000RMB";}}
public class Giant : Buybike{public Giant(){description = "Giant";}public override string Cost(){return "3000RMB";}}

接下去是所有装饰者（配件），全部继承自OtherDecorator

class AddShirt:OtherDecorator{private  Buybike buyBike;public AddShirt(Buybike buyBike){this.buyBike = buyBike;}public override string getDescription(){return buyBike.getDescription() + "Add a shirt";}public override string Cost(){return buyBike.Cost() + "shirt's money:600RMB";}}
class AddShoes:OtherDecorator{private  Buybike buyBike;public AddShoes(Buybike buyBike){this.buyBike = buyBike;}public override string getDescription(){return buyBike.getDescription() + "Add a shoes";}public override string Cost(){return buyBike.Cost() + "shoe's money:300RMB";}}
class AddBag:OtherDecorator{private  Buybike buyBike;public AddBag(Buybike buyBike){this.buyBike = buyBike;}public override string getDescription(){return buyBike.getDescription() + "Add a bag";}public override string Cost(){return buyBike.Cost() + "bag's money:200RMB";}}    

程序运行如下：

    class Program{static void Main(string[] args){Buybike a= new Giant();a = new AddBag(a);a = new AddShirt(a);Console.WriteLine(a.Cost());Console.WriteLine(a.getDescription());}}

此模式好处：装饰者和被装饰者从相同基类派生，类型之间的转化非常方便，适合多态的实现。

具体到例子，此处的a具体到是一个基类变量，把它指到下面的子类不必进行类型转化，而且a具体是什么类型，得在运行时才能确定，程序耦合度大大降低。