设计模式系列之-装饰模式

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;





//装饰模式Demo

namespace DisCountApplication2

{

    class Program

    {

        static void Main(string[] args)

        {

            //优惠方案一

            Order order1 = new Order();

            order1.GoodsTotal = 350;



            OrderDiscount orderDiscount = new OrderDiscount();

            ApplyFullReductionDiscount d1 = new ApplyFullReductionDiscount(100, 10);

            ApplyDiscount d2 = new ApplyDiscount(0.95,200m);

            ApplyDiscount d3 = new ApplyDiscount(0.8);



            Console.WriteLine("\n优惠方案一");

            d1.SetDiscountObject(orderDiscount);

            d2.SetDiscountObject(d1);

            d3.SetDiscountObject(d2);

            d3.Execute(order1);





            //优惠方案二

            Order order2 = new Order();

            order2.GoodsTotal = 150;



            OrderDiscount orderDiscount2 = new OrderDiscount();

            ApplyFullReductionDiscount k1 = new ApplyFullReductionDiscount(100, 9.9m);

            ApplyDiscount k2 = new ApplyDiscount(0.98, 199m);

            ApplyDiscount k3 = new ApplyDiscount(0.88);



            Console.WriteLine("\n优惠方案二");

            k1.SetDiscountObject(orderDiscount2);

            k3.SetDiscountObject(k1);

            k2.SetDiscountObject(k3);

            k2.Execute(order2);

            Console.ReadKey();

        }

    }





    public class Order

    {

        /// <summary>

        /// 商品总价值

        /// </summary>

        public decimal GoodsTotal{get;set;}



        /// <summary>

        /// 扣除折扣，最终客户要付款金额

        /// </summary>

        public decimal GrandTotal{get;set;}

    }



    public interface IOrderDiscount

    {

        void Execute(Order order);

    }



    public class OrderDiscount : IOrderDiscount

    {

        public void Execute(Order order)

        {

            Console.WriteLine("原价为{0}", order.GoodsTotal.ToRoundString());

        }

    }



    public abstract class DiscountBase : IOrderDiscount

    {

        private IOrderDiscount discount = null;



        public  void SetDiscountObject(IOrderDiscount discount)

        {

            this.discount = discount;

        }



        public virtual void Execute(Order order)

        {

            if (discount != null)

            {

               discount.Execute(order);

            }

        }

    }



  

    //满减优惠

    public class ApplyFullReductionDiscount : DiscountBase

    {

        private decimal fullMoney = decimal.Zero;

        private decimal reductionMoney = decimal.Zero;



        public ApplyFullReductionDiscount(decimal fullMoney,decimal reductionMoney)

        {

            this.fullMoney = fullMoney;

            this.reductionMoney = reductionMoney;

        }



        public override void Execute(Order order)

        {

            base.Execute(order);

            if (order.GoodsTotal >= fullMoney)

            {

                order.GoodsTotal = order.GoodsTotal - reductionMoney;

                Console.WriteLine("满{0}减{1}后的金额为{2}", this.fullMoney, this.reductionMoney, order.GoodsTotal.ToRoundString());

                return;

            }

            Console.WriteLine("条件不满足，无法使用满{0}减{1}的优惠", this.fullMoney, this.reductionMoney);

        }

    }



    //打折优惠

    public class ApplyDiscount : DiscountBase

    {

        private double discountRate = 1d;

        private decimal? moneyCondition = null;

        private Order order = null;



        public ApplyDiscount(double discountRate, decimal? moneyCondition)

        {

            this.discountRate = discountRate;

            this.moneyCondition = moneyCondition;

        }



        public ApplyDiscount(double discountRate)

            : this(discountRate,null)

        {



        }



        public override void Execute(Order order)

        {

            this.order = order;

            base.Execute(this.order);

            if (this.moneyCondition != null)

            {

                if (this.order.GoodsTotal >= this.moneyCondition.Value)

                {

                    this.ExecuteDiscount();

                }

                else

                {

                    Console.WriteLine("条件不满足，金额未满{0},无法满足打{1}折的优惠",this.moneyCondition.Value.ToRoundString(), this.discountRate);

                    return;

                }

            }

            else

            {

                this.ExecuteDiscount();

            }

            Console.WriteLine("打{0}折后的金额为{1}", this.discountRate, order.GoodsTotal.ToRoundString());

        }



        private void ExecuteDiscount()

        {

            this.order.GoodsTotal = this.order.GoodsTotal * (decimal)this.discountRate;

        }

    }





    //扩展Decimal类型

    public static class DecimalExtend

    { 

        public static string ToRoundString(this decimal d)

        {

            return Math.Round(d, 2, MidpointRounding.ToEven).ToString("f2");

        }

    }

}