【设计模式】装饰者模式

※文件引自OneDrive，有些人可能看不到

代码如下：

IPrice

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public interface IPrice
    {
        decimal Cost { get; set; }
    }
}

BasePrice

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public class BasePrice : IPrice
    {
        private decimal _cost;

        public decimal Cost
        {
            get
            {
                return _cost;
            }
            set
            {
                _cost = value;
            }
        }
    }
}

TradeDiscountPriceDecorator

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public class TradeDiscountPriceDecorator : IPrice
    {
        private IPrice _basePrice;

        public TradeDiscountPriceDecorator(IPrice price)
        {
            _basePrice = price;
        }

        public decimal Cost
        {
            get
            {
                return _basePrice.Cost * 0.95m;
            }
            set
            {
                _basePrice.Cost = value;
            }
        }
    }
}

CurrencyPriceDecorator

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public class CurrencyPriceDecorator : IPrice
    {
        private IPrice _basePrice;

        private decimal _exchangeRate;

        public CurrencyPriceDecorator(IPrice price, decimal exchangeRate)
        {
            _basePrice = price;
            _exchangeRate = exchangeRate;
        }

        public decimal Cost
        {
            get
            {
                return _basePrice.Cost * _exchangeRate;
            }
            set
            {
                _basePrice.Cost = value;
            }
        }
    }
}

Product

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public class Product
    {
        public IPrice Price { get; set; }
    }
}

ProductService

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public class ProductService
    {
        private IProductRepository _productRepository;

        public ProductService(IProductRepository productRepository)
        {
            _productRepository = productRepository;
        }

        public IEnumerable<Product> GetAllProduct()
        {
            IEnumerable<Product> products = _productRepository.FindAll();

            products.ApplyTradeDiscount();

            products.ApplyCurrencyMultiplier(0.78m);

            return products;
        }
    }
}

IProductRepository

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public interface IProductRepository
    {
        IEnumerable<Product> FindAll();
    }
}

ProductCollectionExtensionMethods

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Model
{
    public static class ProductCollectionExtensionMethods
    {
        public static void ApplyCurrencyMultiplier(this IEnumerable<Product> products, decimal exchangeRate)
        {
            foreach (Product p in products)
            {
                p.Price = new CurrencyPriceDecorator(p.Price, exchangeRate);
            }
        }

        public static void ApplyTradeDiscount(this IEnumerable<Product> products)
        {
            foreach (Product p in products)
            {
                p.Price = new TradeDiscountPriceDecorator(p.Price);
            }
        }
    }
}

---

Program

using DecoratorConsole.Test;
using Model;
using System;
using System.Collections.Generic;

namespace DecoratorConsole
{
    class Program
    {
        static void Main(string[] args)
        {
            ProductService service = new ProductService(new TestPorductRepository());
            IEnumerable<Product> products = service.GetAllProduct();

            foreach (Product p in products)
            {
                Console.WriteLine(string.Format("Product's Price : {0}", p.Price.Cost));
            }

            Console.ReadLine();
        }
    }
}

TestPorductRepository

using Model;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DecoratorConsole.Test
{
    public class TestPorductRepository : IProductRepository
    {
        public IEnumerable<Product> FindAll()
        {
            IEnumerable<Product> products = new Product[] {
                new Product() { Price = new BasePrice() { Cost = 100m }},
                new Product() { Price = new BasePrice() { Cost = 200m }},
                new Product() { Price = new BasePrice() { Cost = 50m }},
                new Product() { Price = new BasePrice() { Cost = 240.5m }},
                new Product() { Price = new BasePrice() { Cost = 500m }},
                new Product() { Price = new BasePrice() { Cost = 1000m }},
                new Product() { Price = new BasePrice() { Cost = 1500m }},
            };

            return products;
        }
    }
}