設計模式：策略模式

策略模式（Strategy）：它定義了算法家族，分別封裝起來，讓它們這件可以相互替換，此模式讓算法的變化，不會影響到使用算法的客戶。

namespace StrategyDesignPattern
{
    //抽象算法類
    public abstract class Strategy
    {
        //算法方法
        public abstract void AlgorithmInterface();
    }
    //具體算法A
    public class ConcreateStrategyA:Strategy
    {
        //算法A實現方法
        public override void AlgorithmInterface()
        {
            Console.WriteLine("算法A實現");
        }
    }
    //具體算法B
    public class ConcreateStrategyB : Strategy
    {
        //算法A實現方法
        public override void AlgorithmInterface()
        {
            Console.WriteLine("算法B實現");
        }
    }
    //上下文
    public class Context
    {
        Strategy Strategy;
        public Context(Strategy strategy)
        {
            Strategy = strategy;
        }
        //上下文接口
        public void ContextInterface()
        {
            Strategy.AlgorithmInterface();
        }
    }
}

測試代碼：

        public void StrategyTest()
        {
            Context context;
            context = new Context(new ConcreateStrategyA());
            context.ContextInterface();

            context = new Context(new ConcreateStrategyB());
            context.ContextInterface();
        }

 策略與簡單工廠結合：

        public Context(string type)
        {
            switch(type)
            {
                case "A":
                    Strategy = new ConcreateStrategyA();
                    break;
                case "B":
                    Strategy = new ConcreateStrategyB();
                    break;
            }
        }