依赖注入机制及IoC的设计与实现

using System;
using System.Web;
using System.Web.Caching;

namespace NGuestBook.Utility
{
    /**//// <summary>
    /// 辅助类，用于缓存操作
    /// </summary>
    public sealed class CacheAccess
    {
        /**//// <summary>
        /// 将对象加入到缓存中
        /// </summary>
        /// <param name="cacheKey">缓存键</param>
        /// <param name="cacheObject">缓存对象</param>
        /// <param name="dependency">缓存依赖项</param>
        public static void SaveToCache(string cacheKey, object cacheObject, CacheDependency dependency)
        {
            Cache cache = HttpRuntime.Cache;
            cache.Insert(cacheKey, cacheObject, dependency);
        }

        /**//// <summary>
        /// 从缓存中取得对象，不存在则返回null
        /// </summary>
        /// <param name="cacheKey">缓存键</param>
        /// <returns>获取的缓存对象</returns>
        public static object GetFromCache(string cacheKey)
        {
            Cache cache = HttpRuntime.Cache;

            return cache[cacheKey];
        }
    }
}

using System;
 using System.Configuration;
 using System.Reflection;
 using System.Web;
 using System.Web.Caching;
 using NGuestBook.Utility;
 
 namespace NGuestBook.Factory
 {
    /**//// <summary>
    /// 依赖注入提供者
    /// 使用反射机制实现
    /// </summary>
    public sealed class DependencyInjector
    {
        /**//// <summary>
        /// 取得数据访问层对象
        /// 首先检查缓存中是否存在，如果不存在，则利用反射机制返回对象
        /// </summary>
        /// <param name="className">数据访问类名称</param>
        /// <returns>数据访问层对象</returns>
        public static object GetDALObject(string className)
        {
            /**//// <summary>
            /// 取得数据访问层名称，首先检查缓存，不存在则到配置文件中读取
            /// 缓存依赖项为Web.Config文件
            /// </summary>
            object dal = CacheAccess.GetFromCache("DAL");
            if (dal == null)
            {
                CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
                dal = ConfigurationManager.AppSettings["DAL"];
                CacheAccess.SaveToCache("DAL", dal, fileDependency);
            }

            /**//// <summary>
            /// 取得数据访问层对象
            /// </summary>
            string dalName = (string)dal;
            string fullClassName = dalName + "." + className;
            object dalObject = CacheAccess.GetFromCache(className);
            if (dalObject == null)
            {
                CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
                dalObject = Assembly.Load(dalName).CreateInstance(fullClassName);
                CacheAccess.SaveToCache(className, dalObject, fileDependency);
            }

            return dalObject;
        }

        /**//// <summary>
        /// 取得业务逻辑层对象
        /// 首先检查缓存中是否存在，如果不存在，则利用反射机制返回对象
        /// </summary>
        /// <param name="className">业务逻辑类名称</param>
        /// <returns>业务逻辑层对象</returns>
        public static object GetBLLObject(string className)
        {
            /**//// <summary>
            /// 取得业务逻辑层名称，首先检查缓存，不存在则到配置文件中读取
            /// 缓存依赖项为Web.Config文件
            /// </summary>
            object bll = CacheAccess.GetFromCache("BLL");
            if (bll == null)
            {
                CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
                bll = ConfigurationManager.AppSettings["BLL"];
                CacheAccess.SaveToCache("BLL", bll, fileDependency);
            }

            /**//// <summary>
            /// 取得业务逻辑层对象
            /// </summary>
            string bllName = (string)bll;
            string fullClassName = bllName + "." + className;
            object bllObject = CacheAccess.GetFromCache(className);
            if (bllObject == null)
            {
                CacheDependency fileDependency = new CacheDependency(HttpContext.Current.Server.MapPath("Web.Config"));
                bllObject = Assembly.Load(bllName).CreateInstance(fullClassName);
                CacheAccess.SaveToCache(className, bllObject, fileDependency);
            }

            return bllObject;
        }
    }
}

using System;
using NGuestBook.IDAL;

namespace NGuestBook.Factory
{
    /**//// <summary>
    /// 数据访问层工厂，用于获取相应的数据访问层对象
    /// 使用Abstract Factory设计模式+Facace设计模式+反射机制+缓存机制设计
    /// </summary>
    public sealed class DALFactory
    {
        /**//// <summary>
        /// 获取管理员数据访问层对象
        /// </summary>
        /// <returns>管理员数据访问层对象</returns>
        public static IAdminDAL CreateAdminDAL()
        {
            return (IAdminDAL)DependencyInjector.GetDALObject("AdminDAL");
        }

        /**//// <summary>
        /// 获取留言数据访问层对象
        /// </summary>
        /// <returns>留言数据访问层对象</returns>
        public static IMessageDAL CreateMessageDAL()
        {
            return (IMessageDAL)DependencyInjector.GetDALObject("MessageDAL");
        }

        /**//// <summary>
        /// 获取评论数据访问层对象
        /// </summary>
        /// <returns>评论数据访问层对象</returns>
        public static ICommentDAL CreateCommentDAL()
        {
            return (ICommentDAL)DependencyInjector.GetDALObject("CommentDAL");
        }
    }
}

using System;
using NGuestBook.IBLL;

namespace NGuestBook.Factory
{
    /**//// <summary>
    /// 业务逻辑层工厂，用于获取相应的业务逻辑层对象
    /// 使用Abstract Factory设计模式+Facace设计模式+反射机制+缓存机制设计
    /// </summary>
    public sealed class BLLFactory
    {
        /**//// <summary>
        /// 获取管理员业务逻辑层对象
        /// </summary>
        /// <returns>管理员业务逻辑层对象</returns>
        public static IAdminBLL CreateAdminBLL()
        {
            return (IAdminBLL)DependencyInjector.GetBLLObject("AdminBLL");
        }

        /**//// <summary>
        /// 获取留言业务逻辑层对象
        /// </summary>
        /// <returns>留言业务逻辑层对象</returns>
        public static IMessageBLL CreateMessageBLL()
        {
            return (IMessageBLL)DependencyInjector.GetBLLObject("MessageBLL");
        }

        /**//// <summary>
        /// 获取评论业务逻辑层对象
        /// </summary>
        /// <returns>评论业务逻辑层对象</returns>
        public static ICommentBLL CreateCommentBLL()
        {
            return (ICommentBLL)DependencyInjector.GetBLLObject("CommentBLL");
        }
    }
}