讲解C#设计模式编程中享元模式的运用

 /// 
 /// 客户端调用 /// 
 class Client { static void Main(string[] args) { // 定义外部状态，例如字母的位置等信息 int externalstate = 10; // 初始化享元工厂 FlyweightFactory factory = new FlyweightFactory(); // 判断是否已经创建了字母A，如果已经创建就直接使用创建的对象A Flyweight fa = factory.GetFlyweight("A"); if (fa != null) { // 把外部状态作为享元对象的方法调用参数 fa.Operation(--externalstate); } // 判断是否已经创建了字母B Flyweight fb = factory.GetFlyweight("B"); if (fb != null) { fb.Operation(--externalstate); } // 判断是否已经创建了字母C Flyweight fc = factory.GetFlyweight("C"); if (fc != null) { fc.Operation(--externalstate); } // 判断是否已经创建了字母D Flyweight fd= factory.GetFlyweight("D"); if (fd != null) { fd.Operation(--externalstate); } else { Console.WriteLine("驻留池中不存在字符串D"); // 这时候就需要创建一个对象并放入驻留池中 ConcreteFlyweight d = new ConcreteFlyweight("D"); factory.flyweights.Add("D", d); } Console.Read(); } } /// 
 /// 享元工厂，负责创建和管理享元对象 /// 
 public class FlyweightFactory { // 最好使用泛型Dictionary //public Dictionary flyweights = new Dictionary(); public Hashtable flyweights = new Hashtable(); public FlyweightFactory() { flyweights.Add("A", new ConcreteFlyweight("A")); flyweights.Add("B", new ConcreteFlyweight("B")); flyweights.Add("C", new ConcreteFlyweight("C")); } public Flyweight GetFlyweight(string key) { // 更好的实现如下 //Flyweight flyweight = flyweights[key] as Flyweight; //if (flyweight == null) //{ // Console.WriteLine("驻留池中不存在字符串" + key); // flyweight = new ConcreteFlyweight(key); //} //return flyweight; return flyweights[key] as Flyweight; } } /// 
 /// 抽象享元类，提供具体享元类具有的方法 /// 
 public abstract class Flyweight { public abstract void Operation(int extrinsicstate); } // 具体的享元对象，这样我们不把每个字母设计成一个单独的类了，而是作为把共享的字母作为享元对象的内部状态 public class ConcreteFlyweight : Flyweight { // 内部状态 private string intrinsicstate ; // 构造函数 public ConcreteFlyweight(string innerState) { this.intrinsicstate = innerState; } /// 
 /// 享元类的实例方法 /// 
 /// 外部状态 public override void Operation(int extrinsicstate) { Console.WriteLine("具体实现类: intrinsicstate {0}, extrinsicstate {1}", intrinsicstate, extrinsicstate); } }