讲解C#设计模式编程中享元模式的运用

/// <summary> /// 客户端调用 /// </summary> 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();  } } /// <summary> /// 享元工厂，负责创建和管理享元对象 /// </summary> public class FlyweightFactory {  // 最好使用泛型Dictionary<string,Flyweighy>  //public Dictionary<string, Flyweight> flyweights = new Dictionary<string, Flyweight>();  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;  } } /// <summary> /// 抽象享元类，提供具体享元类具有的方法 /// </summary> 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;  }  /// <summary>  /// 享元类的实例方法  /// </summary>  /// <param name="extrinsicstate">外部状态</param>  public override void Operation(int extrinsicstate)  {   Console.WriteLine("具体实现类: intrinsicstate {0}, extrinsicstate {1}", intrinsicstate, extrinsicstate);  } }