设计模式-策略模式

定义：

策略模式定义了一系列的算法，并将每一个算法封装起来，使它们可以互相替换

个人理解：

类似委托的作用，将算法通过客户端传入，起到订制的作用

客户端：

IActive active = new HighActive();
decimal payPrice = new ActiveExecutor().Execute(active);

策略执行类：

    public class ActiveExecutor
    {
        public decimal Execute(IActive active)
        {
            decimal orderPrice = 200M;
            return active.Rule(orderPrice);
        }
    }

策略类：

    public interface IActive
    {
        //int DiscountType { get; }
        decimal Rule(decimal orderPrice);
    }
    public class LowActive : IActive
    {
        public decimal Rule(decimal orderPrice)
        {
            if (orderPrice < 100M)
            {
                return orderPrice - 1M;
            }
            else
            {
                return orderPrice - 5M;
            }
        }
    }
    public class MiddleActive : IActive
    {
        public decimal Rule(decimal orderPrice)
        {
            if (orderPrice < 100M)
            {
                return orderPrice - 10M;
            }
            else
            {
                return orderPrice - 20M;
            }
        }
    }
    public class HighActive : IActive
    {
        public decimal Rule(decimal orderPrice)
        {
            if (orderPrice < 100M)
            {
                return orderPrice - 20M;
            }
            else
            {
                return orderPrice - 50M;
            }
        }
    }