设计模式：享元模式

享元模式（Flyweight）：运用共享技术有效地支持大量细粒度的对象。

namespace FlyDesign
{
    public abstract class Flyweight
    {
        public abstract void Operation(int extrinsicstate);
    }
    public class ConcreteFlyweight : Flyweight
    {
        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("具体Flyweight:" + extrinsicstate);
        }
    }
    public class UnsharedConcretFlyweight : Flyweight
    {
        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("不共享的具体Flyweight:" + extrinsicstate);
        }
    }
    public class FlyweightFactory
    {
        private Hashtable flyweights = new Hashtable();
        public FlyweightFactory()
        {
            flyweights.Add("X", new ConcreteFlyweight());
            flyweights.Add("Y", new ConcreteFlyweight());
            flyweights.Add("Z", new ConcreteFlyweight());
        }
        public Flyweight GetFlyweight(string key)
        {
            return (Flyweight)flyweights[key];
        }
    }
}

测试代码：

            int extrinsicstate = 22;
            FlyweightFactory f = new FlyweightFactory();
            Flyweight fx = f.GetFlyweight("X");
            fx.Operation(--extrinsicstate);
            Flyweight fy = f.GetFlyweight("Y");
            fy.Operation(--extrinsicstate);
            Flyweight fz = f.GetFlyweight("Z");
            fz.Operation(--extrinsicstate);
            Flyweight uf = new UnsharedConcretFlyweight();
            uf.Operation(--extrinsicstate);