享元模式（Flyweight）

享元模式：应用共享技术有效支持大量细粒度的对象。

namespace FlyWeightPattern
{
    //2017.07.01 14:22 by ldb
    //享元基类
    abstract class FlyWeight
    {
        public abstract void Operation(int extrinsicstate);
    }

    class ConcreteFlyWeight : FlyWeight
    {
        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("具体FlyWeight:" + extrinsicstate);
        }
    }
    /// <summary>
    /// 不需要共享的FlyWeight子类
    /// </summary>
    class UshareConcreteFlyWeight : FlyWeight
    {
        public override void Operation(int extrinsicstate)
        {
            Console.WriteLine("不共享的具体FlyWeight:" + extrinsicstate);
        }
    }

    class FlyWeightFactory//享元工厂。
    {
        private Hashtable flyweights = new Hashtable();

        public FlyWeightFactory()
        {
            flyweights.Add("x", new ConcreteFlyWeight());
            flyweights.Add("y", new ConcreteFlyWeight());
            flyweights.Add("", new ConcreteFlyWeight());
        }

        public FlyWeight GetFlyWeight(string key)
        {
            return (FlyWeight)flyweights[key];
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            int extrinsicstate = 22;

            FlyWeightFactory fact = new FlyWeightFactory();

            FlyWeight fx = fact.GetFlyWeight("x");
            fx.Operation(--extrinsicstate);

            FlyWeight fy = fact.GetFlyWeight("y");
            fy.Operation(--extrinsicstate);

            FlyWeight uf = new UshareConcreteFlyWeight();
            uf.Operation(--extrinsicstate);

            Console.ReadKey();
        }
    }
}