享元模式：運用共享技術有效地支持大量細粒度的對象。

    /// <summary>
    ///  抽象享元類，提供具體享元類具有的方法
    /// </summary>
    public abstract class Flyweight
    {
        public abstract void Operation(int extrinsicstate);
    }

    // 具體的享元對象，這樣我們不把每個字母設計成一個單獨的類了，而是作為把共享的字母作為享元對象的內部狀態
    public class ConcreteFlyweight : Flyweight
    {
        
 
// 內部狀態
        private string intrinsicstate ;

        // 構造函數
        public ConcreteFlyweight(string innerState)
        {
            this.intrinsicstate = innerState;
        }

        /// <summary>
        /// 享元類的實例方法
        /// </summary>
        /// <param name="extrinsicstate">外部狀態</param>
 

        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("具體實現類: intrinsicstate {0}, extrinsicstate {1}", intrinsicstate, extrinsicstate);
        }
    }


 /// <summary>
    /// 享元工廠，負責創建和管理享元對象
    /// </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)
        {
            // 更好的實現如下
            //Flyweight flyweight = flyweights[key] as Flyweight;
            //if (flyweight == null)
            //{
            //    Console.WriteLine("駐留池中不存在字符串" + key);
            //    flyweight = new ConcreteFlyweight(key);
            //}
            //return flyweight;
return flyweights[key] as Flyweight;
        }
    }


/// <summary>
    /// 客戶端調用
    /// </summary>
    class Client
    {
        static void Main(string[] args)
        {
            // 定義外部狀態，例如字母的位置等信息
            int externalstate = 10;
            // 初始化享元工廠
            FlyweightFactory factory = new FlyweightFactory();

            // 判斷是否已經創建了字母A，如果已經創建就直接使用創建的對象A
            Flyweight fa = factory.GetFlyweight("A");
            if (fa != null)
            {
                // 把外部狀態作為享元對象的方法調用參數
                fa.Operation(--externalstate);
            }
            // 判斷是否已經創建了字母B
            Flyweight fb = factory.GetFlyweight("B");
            if (fb != null)
            {
                fb.Operation(--externalstate);
            }
            // 判斷是否已經創建了字母C
            Flyweight fc = factory.GetFlyweight("C");
            if (fc != null)
            {
                fc.Operation(--externalstate);
            }
            // 判斷是否已經創建了字母D
            Flyweight fd= factory.GetFlyweight("D");
            if (fd != null)
            {
                fd.Operation(--externalstate);
            }
            else
            {
                Console.WriteLine("駐留池中不存在字符串D");
                // 這時候就需要創建一個對象並放入駐留池中
                ConcreteFlyweight d = new ConcreteFlyweight("D");
                factory.flyweights.Add("D", d);
            }

            Console.Read();
        }
    }

   
    

代碼參考：http://www.cnblogs.com/zhili/p/FlyweightPattern.html

享元模式