我对petshop4的简单理解！[通俗易懂]

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petshop4充分体现了面向接口编程的思想，就是给你一个接口你别管我是怎么实现的，你只管用别说其他的。

namespace PetShop.BLL {

    /// <summary>     /// A business component to manage products     /// </summary>     public class Product {

        // Get an instance of the Product DAL using the DALFactory         // Making this static will cache the DAL instance after the initial load         private static readonly IProduct dal = PetShop.DALFactory.DataAccess.CreateProduct();

在bll层，这里使用创建Produce的接口，你只管调用他的方法。

namespace PetShop.IDAL{    /// <summary>  /// Interface for the Product DAL  /// </summary>  public interface IProduct{     /// <summary>   /// Method to search products by category name   /// </summary>   /// <param name=”category”>Name of the category to search by</param>         /// <returns>Interface to Model Collection Generic of search results</returns>   IList<ProductInfo> GetProductsByCategory(string category); 

  /// <summary>   /// Method to search products by a set of keyword   /// </summary>   /// <param name=”keywords”>An array of keywords to search by</param>   /// <returns>Interface to Model Collection Generic of search results</returns>         IList<ProductInfo> GetProductsBySearch(string[] keywords);

  /// <summary>   /// Query for a product   /// </summary>   /// <param name=”productId”>Product Id</param>   /// <returns>Interface to Model ProductInfo for requested product</returns>   ProductInfo GetProduct(string productId);  }

这里是定义了Product接口和他的虚方法。

namespace PetShop.SQLServerDAL {

    public class Product : IProduct {

        //Static constants         private const string SQL_SELECT_PRODUCTS_BY_CATEGORY = “SELECT Product.ProductId, Product.Name, Product.Descn, Product.Image, Product.CategoryId FROM Product WHERE Product.CategoryId = @Category”;         private const string SQL_SELECT_PRODUCTS_BY_SEARCH1 = “SELECT ProductId, Name, Descn, Product.Image, Product.CategoryId FROM Product WHERE ((“;         private const string SQL_SELECT_PRODUCTS_BY_SEARCH2 = “LOWER(Name) LIKE ‘%’ + {0} + ‘%’ OR LOWER(CategoryId) LIKE ‘%’ + {0} + ‘%'”;         private const string SQL_SELECT_PRODUCTS_BY_SEARCH3 = “) OR (“;         private const string SQL_SELECT_PRODUCTS_BY_SEARCH4 = “))”;         private const string SQL_SELECT_PRODUCT = “SELECT Product.ProductId, Product.Name, Product.Descn, Product.Image, Product.CategoryId FROM Product WHERE Product.ProductId  = @ProductId”;         private const string PARM_CATEGORY = “@Category”;         private const string PARM_KEYWORD = “@Keyword”;         private const string PARM_PRODUCTID = “@ProductId”;

        /// <summary>         /// Query for products by category         /// </summary>         /// <param name=”category”>category name</param>          /// <returns>A Generic List of ProductInfo</returns>         public IList<ProductInfo> GetProductsByCategory(string category) {

            IList<ProductInfo> productsByCategory = new List<ProductInfo>();

这里是实现Product接口的类，

namespace PetShop.DALFactory {

    /// <summary>     /// This class is implemented following the Abstract Factory pattern to create the DAL implementation     /// specified from the configuration file     /// </summary>     public sealed class DataAccess {

        // Look up the DAL implementation we should be using         private static readonly string path = ConfigurationManager.AppSettings[“WebDAL”];         private static readonly string orderPath = ConfigurationManager.AppSettings[“OrdersDAL”];                 private DataAccess() { }

        public static PetShop.IDAL.ICategory CreateCategory() {             string className = path + “.Category”;             return (PetShop.IDAL.ICategory)Assembly.Load(path).CreateInstance(className);         }

这里是利用工厂模式来映射你需要你想创建哪一个。

后面还有一些消息队列MSMQMessage利用cache缓存以后达到异步处理购物车里订单的功能！

刚开始看应先从先从Product入口，关于Product的一些操作串联起来看一遍！