1.定义接口

using System;using System.Collections.Generic;using System.Linq;using System.Web;namespace EssentialTools.Models{    public interface IValueCalculator    {        decimal ValueProducts(IEnumerable
    
      products);    }}
    

2.继承接口

using System;using System.Collections.Generic;using System.Linq;using System.Web;namespace EssentialTools.Models{    public class LinqValueCalculator : IValueCalculator    {        public decimal ValueProducts(IEnumerable
    
      products)        {            return products.Sum(p => p.Price);        }    }}
    

3.购物车,商品对象，计算商品总价方法

using System;using System.Collections.Generic;using System.Linq;using System.Web;namespace EssentialTools.Models{    public class ShoppingCart    {        private IValueCalculator calc;        public ShoppingCart(IValueCalculator calcParam)        {            calc = calcParam; // 引入其他类帮助        }        public IEnumerable
    
      Products { get; set; }        public decimal CalculateProductTotal()        {            return calc.ValueProducts(Products);        }    }}
    

4.控制器整合处理

private Product[] products = {            new Product {Name = "Kayak", Category = "Watersports", Price = 275M},            new Product {Name = "Lifejacket", Category = "Watersports", Price = 48.95M},            new Product {Name = "Soccer ball", Category = "Soccer", Price = 19.50M},            new Product {Name = "Corner flag", Category = "Soccer", Price = 34.95M}        };        public ActionResult Index()        {            IValueCalculator calc = new LinqValueCalculator();            ShoppingCart cart = new ShoppingCart(calc) { Products = products }; // 购物车中的商品            decimal totalValue = cart.CalculateProductTotal();            return View(totalValue);        }

5.页面展示

@model decimal@{    Layout = null;}    
            
    
             Total value is $@Model    
    

</html>