ASP.net网站开发四“酷”全书：新闻、论坛、电子商城、博客_源码

				using System;
				using System.Reflection;
				using System.Configuration;
				using System.Security.Policy;
				
				namespace BookShop.DALFactory {
				
					/// 
					/// Factory implementaion for the Product DAL object
					/// 
					public class Product {
				
						public static BookShop.IDAL.IProduct Create() {
							
							/// Look up the DAL implementation we should be using
							string path = System.Configuration.ConfigurationSettings.AppSettings["WebDAL"];
							string className = path + ".Product";
				
							// Using the evidence given in the config file load the appropriate assembly and class
							return (BookShop.IDAL.IProduct)Assembly.Load(path).CreateInstance(className);
						}
					}
				}