Asp.Net数据库缓存依赖

1.为数据库启用缓存依赖(您需要具有管理特权，或管理帐户和密码。)

在"Visual Studio 命令提示(2010(这里我用的是2010版本的,可以使用VS2005)"运行aspnet_regsql

(MSSQL 2000启用方式略有不同)

aspnet_regsql.exe -S Excel-lang -U sa -P sa -ed -d TestDB -et -t UserInfo

或者

aspnet_regsql -C "data source=Excel-lang;initial catalog=TestDB;user id=sa;password=sa" -ed -et -t "UserInfos"

注:1.数据库服务器名称为 Excel-lang 2.用户和密码为 sa sa 3.数据库和表分别为 TestDB UserInfo
运行完成后会在数据库下面产生一张表AspNet_SqlCacheTablesForChangeNotification和一个触发器

2.检查数据库是否启用监听服务

Select DataBasePropertyex('TestDB','IsBrokerEnabled')

或者

SELECT is_broker_enabled FROM sys.databases WHERE name = 'TestDB'

(1为已启用,0为未启用)

如果没有启用

使用语句ALTER DATABASE TestDB SET ENABLE_BROKER;启用监听服务

如果启用失败或者很长时间一直在执行请执行一下语句

ALTER DATABASE TestDB SET NEW_BROKER WITH ROLLBACK IMMEDIATE;

ALTER DATABASE TestDB SET ENABLE_BROKER;

3.配置WebConfig

<configuration>
 <connectionStrings>节点下配置

<add name="TestDBConnectionString" connectionString="Data Source=EXCEL-LANG;Initial Catalog=TestDB;Persist Security Info=True;User ID=sa;Password=sa" providerName="System.Data.SqlClient" />
  </connectionStrings>

 <system.web>   节点下配置

 <caching>
      <sqlCacheDependency enabled="true" pollTime="1000">
        <databases>
          <add name="TestDB" connectionStringName="TestDBConnectionString"/>
        </databases>
      </sqlCacheDependency>
    </caching>

各节点属性请参照MSDN相关文档

4.页面加载时执行以下代码,从数据库中获取数据并加入缓存中

        List<UserInfo> list = DataCache.GetCache("UserInfoCache") as List<UserInfo>;
        if (list == null)
        {
            System.Web.Caching.SqlCacheDependency dep = new System.Web.Caching.SqlCacheDependency("TestDB", "UserInfo");
            list = userManger.GetUserLoginList();
            onMoveBack = new CacheItemRemovedCallback(RemovedCallback);
            DataCache.SetCache("UserInfoCache", list, dep, onMoveBack);
        }

5.申明缓存失效后所执行的函数

   CacheItemRemovedCallback onMoveBack;
    private void RemovedCallback(String k, Object v, CacheItemRemovedReason r)
    {
        onMoveBack = new CacheItemRemovedCallback(RemovedCallback);
        System.Web.Caching.SqlCacheDependency dep = new System.Web.Caching.SqlCacheDependency("TestDB", "UserInfo");
        List<UserInfo> list = userManger.GetUserLoginList();//从数据库中获取数据
      DataCache.SetCache("UserInfoCache", list, dep,onMoveBack);
    }

6.DataCache类 

using System;
using System.Collections.Generic;
using System.Text;
using System.Web;
using System.Data;
using System.Data.SqlClient;
using System.Web.Caching;

public class DataCache
{
    /// <summary> 
    /// 获取当前应用程序指定CacheKey的Cache值 
    /// </summary> 
    /// <param name="CacheKey"></param> 
    /// <returns></returns> 
    public static object GetCache(string CacheKey)
    {
        System.Web.Caching.Cache objCache = HttpRuntime.Cache;
        return objCache[CacheKey];
    }
    /// <summary> 
    /// 设置当前应用程序指定CacheKey的Cache值 
    /// </summary> 
    /// <param name="CacheKey"></param> 
    /// <param name="objObject"></param> 
    public static void SetCache(string CacheKey, object objObject)
    {
        System.Web.Caching.Cache objCache = HttpRuntime.Cache;
        objCache.Insert(CacheKey, objObject);
    }
    /// <summary> 
    /// 设置已缓存依赖的方式缓存数据 
    /// </summary> 
    /// <param name="CacheKey">键值</param> 
    /// <param name="objObject">缓存对象</param> 
    /// <param name="dep">缓存依赖项</param> 
    /// <param name="onMoveCallBack">缓存项移除是触发的回调函数</param> 
    public static void SetCache(string CacheKey, object objObject, System.Web.Caching.CacheDependency dep, CacheItemRemovedCallback onMoveCallBack)
    {
        System.Web.Caching.Cache objCache = HttpRuntime.Cache;
        objCache.Insert(
        CacheKey,
        objObject,
        dep,
        System.Web.Caching.Cache.NoAbsoluteExpiration,//从不过期 
        System.Web.Caching.Cache.NoSlidingExpiration,//禁用可调过期 
        System.Web.Caching.CacheItemPriority.Default,
        onMoveCallBack
        );
    }
}

7.执行步骤为从数据库查询数据→加入缓存(同时设置过期策略以及过期回调函数)→过期时→执行过期回调函数

 RemovedCallback→重新查询数据并加入缓存.

缓存依赖是