策略模式，定义一系列算法类，将每一个算法封装起来，并让他们可以相互替换。策略模式是把算法独立出来，让用户选择使用

 interface IStrategy
    {
        void Algorithm();
    }

    class ConcreteStrategyA:IStrategy
    {
        public void Algorithm()
        {
            Console.WriteLine("使用A算法");
        }
    }

    class ConcreteStrategyB : IStrategy
    {
        public void Algorithm()
        {
            Console.WriteLine("使用B算法");
        }
    }

    //环境上下文
    class Context
    {
        private IStrategy strategy;
        public Context(IStrategy strategy)
        {
            this.strategy = strategy;
        }

        public void Algorithm()
        {
            strategy.Algorithm();
        }
    
    }

    class Program
    {
        static void Main()
        {
            IStrategy strategy = new ConcreteStrategyA();
            Context context = new Context(strategy);
            context.Algorithm();
            Console.Read();

        }

    }