<configSections>      <section name="DistributedReadWriteSection" type="Project.DistributedReadWriteForEF.DistributedReadWriteSectionHandler, Project.DistributedReadWriteForEF"/>  </configSections>  <DistributedReadWriteSection>    <add key="readDb1" Ip="192.168.2.71" Port="1433" DbName="background_read1" UserId="sa" Password="zzl123" />    <add key="readDb2" Ip="192.168.2.71" Port="1433" DbName="TestWrite_Read_Zzl" UserId="sa" Password="zzl123" />    <add key="readDb3" Ip="192.168.2.29" Port="1433" DbName="TestWrite_Read_Zzl" UserId="sa" Password="1" />  </DistributedReadWriteSection>  <appSettings>    <!-- 只读服务器的sql连接串配置模版-->    <add key ="readDbConnection" value=http://www.mamicode.com/"data source={0};initial catalog={1};persist security info=True;user id={2};password={3};multipleactiveresultsets=True;application name=EntityFramework"/>    <add key ="writeDbConnection" value=http://www.mamicode.com/"data source=.;initial catalog=background;persist security info=True;user id=sa;password=zzl123;multipleactiveresultsets=True;application name=EntityFramework"/>  </appSettings>

  /// <summary>    /// redis配置信息加载    /// </summary>    internal class DistributedReadWriteManager    {        /// <summary>        /// 配置信息实体        /// </summary>        public static IList<DistributedReadWriteSection> Instance        {            get            {                return GetSection();            }        }        private static IList<DistributedReadWriteSection> GetSection()        {            var dic = ConfigurationManager.GetSection("DistributedReadWriteSection") as Dictionary<string, DistributedReadWriteSection>;            return dic.Values.ToList();        }    }

    /// <summary>    /// DistributedReadWriteForEFSection块，在web.config中提供DistributedReadWriteForEFSection块定义    /// </summary>    internal class DistributedReadWriteSection : ConfigurationSection    {        /// <summary>        /// 主机地址        /// </summary>        [ConfigurationProperty("Ip", DefaultValue = http://www.mamicode.com/"127.0.0.1")]        public string Ip        {            get { return (string)this["Ip"]; }            set { this["Ip"] = value; }        }        /// <summary>        /// 端口号        /// </summary>        [ConfigurationProperty("Port", DefaultValue = http://www.mamicode.com/"1433")]        public int Port        {            get { return (int)this["Port"]; }            set { this["Port"] = value; }        }        /// <summary>        /// 数据库名称        /// </summary>        [ConfigurationProperty("DbName", DefaultValue = http://www.mamicode.com/"Test")]        public string DbName        {            get { return (string)this["DbName"]; }            set { this["DbName"] = value; }        }        /// <summary>        /// 数据库账号        /// </summary>        [ConfigurationProperty("UserId", DefaultValue = http://www.mamicode.com/"sa")]        public string UserId        {            get { return (string)this["UserId"]; }            set { this["UserId"] = value; }        }        /// <summary>        /// 数据库账号        /// </summary>        [ConfigurationProperty("Password", DefaultValue = http://www.mamicode.com/"sa")]        public string Password        {            get { return (string)this["Password"]; }            set { this["Password"] = value; }        }    }

    internal class DistributedReadWriteSectionHandler : IConfigurationSectionHandler    {        #region IConfigurationSectionHandler 成员        public object Create(object parent, object configContext, System.Xml.XmlNode section)        {            Dictionary<string, DistributedReadWriteSection> names = new Dictionary<string, DistributedReadWriteSection>();            string _key = string.Empty;            string _ip = string.Empty;            string _dbName = string.Empty;            string _userId = string.Empty;            string _password = string.Empty;            int _port = 1433;            foreach (XmlNode childNode in section.ChildNodes)            {                if (childNode.Attributes["key"] != null)                {                    _key = childNode.Attributes["key"].Value;                    if (childNode.Attributes["Ip"] != null)                    {                        _ip = childNode.Attributes["Ip"].Value;                    }                    if (childNode.Attributes["Port"] != null)                    {                        _port = Convert.ToInt32(childNode.Attributes["Port"].Value);                    }                    if (childNode.Attributes["DbName"] != null)                    {                        _dbName = childNode.Attributes["DbName"].Value;                    }                    if (childNode.Attributes["UserId"] != null)                    {                        _userId = childNode.Attributes["UserId"].Value;                    }                    if (childNode.Attributes["Password"] != null)                    {                        _password = childNode.Attributes["Password"].Value;                    }                    names.Add(_key, new DistributedReadWriteSection { Ip = _ip, Port = _port, DbName = _dbName, UserId = _userId, Password = _password });                }            }            return names;        }        #endregion    }

   public static void UsingNoMsdtc(IUnitOfWork db, bool isOutest, Action action)        {            var objectContext = ((System.Data.Entity.Infrastructure.IObjectContextAdapter)db).ObjectContext;            try            {                objectContext.Connection.Close();                //强制将所有curd操作维持到主库                Project.DistributedReadWriteForEF.CommandInterceptor.IsTransactionScope = true;                //重新设置链接串                if (System.Configuration.ConfigurationManager.AppSettings["writeDbConnection"] != null)                    objectContext.TransactionHandler.DbContext.Database.Connection.ConnectionString = System.Configuration.ConfigurationManager.AppSettings["writeDbConnection"];                objectContext.Connection.Open();                using (TransactionScope trans = new TransactionScope())                {                    action();                    trans.Complete();                    Project.DistributedReadWriteForEF.CommandInterceptor.IsTransactionScope = false;//事务结束将走读写分离                }            }            finally            {                if (isOutest)//如果是最外层事务，再将连接关闭！内部事务与外部事务需要共用一个Connection的连接                    objectContext.Connection.Close(); //只能关闭,不能dispose,因为dispose之后,上下文就无法得到链接串了            }        }

    /// <summary>    /// SQL命令拦截器    /// 主要实现EF的读写分离    /// </summary>    public class CommandInterceptor : DbCommandInterceptor    {        static CommandInterceptor()        {            readConnList = DistributedReadWriteManager.Instance;            sysTimer.Enabled = true;            sysTimer.Elapsed += sysTimer_Elapsed;            sysTimer.Start();        }        /// <summary>        /// 是否在一个事务中，如果是select,insert,update,delete都走主库        /// ThreadStatic标识它只在当前线程有效        /// </summary>        [ThreadStatic]        public static bool IsTransactionScope = false;        /// <summary>        /// 锁住它        /// </summary>        private static object lockObj = new object();        /// <summary>        /// 定期找没有在线的数据库服务器        /// </summary>        private static Timer sysTimer = new Timer(5000);        /// <summary>        ///　读库，从库集群，写库不用设置走默认的EF框架        /// </summary>        private static IList<DistributedReadWriteSection> readConnList;        #region Private Methods        private static void sysTimer_Elapsed(object sender, ElapsedEventArgs e)        {            if (readConnList != null && readConnList.Any())            {                foreach (var item in readConnList)                {                    //心跳测试，将死掉的服务器IP从列表中移除                    var client = new TcpClient();                    try                    {                        client.Connect(new IPEndPoint(IPAddress.Parse(item.Ip), item.Port));                    }                    catch (SocketException)                    {                        //异常，没有连接上                        readConnList.Remove(item);                    }                    if (!client.Connected)                    {                        readConnList.Remove(item);                    }                }            }        }        /// <summary>        /// 处理读库字符串        /// </summary>        /// <returns></returns>        private string GetReadConn()        {            if (readConnList != null && readConnList.Any())            {                var resultConn = readConnList[Convert.ToInt32(Math.Floor((double)new Random().Next(0, readConnList.Count)))];                return string.Format(System.Configuration.ConfigurationManager.AppSettings["readDbConnection"]                    , resultConn.Ip                    , resultConn.DbName                    , resultConn.UserId                    , resultConn.Password);            }            return string.Empty;        }        /// <summary>        /// 只读库的选择,加工command对象        /// 说明：事务中,所有语句都走主库，事务外select走读库,insert,update,delete走主库        /// 希望：一个ＷＥＢ请求中，读与写的仓储使用一个，不需要在程序中去重新定义        /// </summary>        /// <param name="command"></param>        private void ReadDbSelect(DbCommand command)        {            if (!string.IsNullOrWhiteSpace(GetReadConn()))//如果配置了读写分离，就去实现            {                command.Connection.Close();                if (!command.CommandText.StartsWith("insert", StringComparison.InvariantCultureIgnoreCase) && !IsTransactionScope)                    command.Connection.ConnectionString = GetReadConn();                command.Connection.Open();            }        }        #endregion        #region Override Methods        /// <summary>        /// Linq to Entity生成的update,delete        /// </summary>        /// <param name="command"></param>        /// <param name="interceptionContext"></param>        public override void NonQueryExecuting(DbCommand command, DbCommandInterceptionContext<int> interceptionContext)        {            base.NonQueryExecuting(command, interceptionContext);//update,delete等写操作直接走主库        }        /// <summary>        /// 执行sql语句，并返回第一行第一列，没有找到返回null,如果数据库中值为null，则返回 DBNull.Value        /// </summary>        /// <param name="command"></param>        /// <param name="interceptionContext"></param>        public override void ScalarExecuting(DbCommand command, DbCommandInterceptionContext<object> interceptionContext)        {            ReadDbSelect(command);            base.ScalarExecuting(command, interceptionContext);        }        /// <summary>        /// Linq to Entity生成的select,insert        /// 发送到sqlserver之前触发        /// warning:在select语句中DbCommand.Transaction为null，而ef会为每个insert添加一个DbCommand.Transaction进行包裹        /// </summary>        /// <param name="command"></param>        /// <param name="interceptionContext"></param>        public override void ReaderExecuting(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)        {            ReadDbSelect(command);            base.ReaderExecuted(command, interceptionContext);        }        /// <summary>        /// 发送到sqlserver之后触发        /// </summary>        /// <param name="command"></param>        /// <param name="interceptionContext"></param>        public override void ReaderExecuted(DbCommand command, DbCommandInterceptionContext<DbDataReader> interceptionContext)        {            base.ReaderExecuted(command, interceptionContext);        }        #endregion    }