SqlDataReader 的释放

Question

我有一个承包商，当我们执行 sql 查询时，他到处写这样的代码：

sql.Append(string.Format("SELECT TableId FROM ps_SavedTables WHERE guid = '{0}'", guid));

        using (IDataReader reader = SqlHelper.GetDataReader(sql.ToString())) {
            if (reader.Read()) {
                result = reader.IsDBNull(0) ? string.Empty : reader[0].ToString();
            }
            //CDW added to close SqlDataReader
            reader.Close();
        }

GetDataReader 类位于 App_Code 帮助文件中，声明如下：

 public static SqlDataReader GetDataReader(string sql) {
        return GetDataReader(sql, DefaultConnectionString);
    }

    public static SqlDataReader GetDataReader(string sql, int connectionTime) {
        return GetDataReader(sql, DefaultConnectionString, connectionTime);
    }

    /// <summary>
    /// Executes DB command ExecutedReader and returns the DataReader
    /// </summary>
    /// <param name="sql">SQL statement(s) to be used with DB command</param>
    /// <param name="connectionString">Database connection string</param>
    /// <returns>DataReader containing results of supplied SQL statement(s)</returns>
    public static SqlDataReader GetDataReader(string sql, string connectionString) {
        lock (_lock) {
            SqlConnection connection = null;
            try {
                connection = GetConnection(connectionString);
                //connection.Open();
                using (SqlCommand cmd = new SqlCommand(sql, connection)) {
                    WriteDebugInfo("GetDataReader", sql);
                    return cmd.ExecuteReader(CommandBehavior.CloseConnection);
                }
            }
            catch (Exception e) {
                if (connection != null)
                    connection.Dispose();
                throw new DataException(sql, connectionString, e);
            }

        }
    }

然后我在本地运行我的代码（它为统计数据执行了大量 SQL）并在两个不同的浏览器中运行相同类型的东西，其中 1 个浏览器总是在这里崩溃：

Server.ScriptTimeout = 300;
        string returnCode = string.Empty;
        using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["MainDll"].ToString())) {
            connection.Open();
            using (SqlCommand command = new SqlCommand(sql.ToString(), connection)) {
                command.CommandType = CommandType.Text;
                command.CommandTimeout = 300;
                returnCode = (string)command.ExecuteScalar();
                Dispose();
            }
            Dispose();
        }

堆栈是这样的：

.NET Framework execution was aborted by escalation policy because of out of memory. 
System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.
System.InvalidOperationException: 
  at System.Data.SqlClient.SqlInternalConnectionSmi.ValidateConnectionForExecute(SqlCommand command)
  at System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute(String method, SqlCommand command)
  at System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async)
  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
  at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
  at System.Data.SqlClient.SqlCommand.ExecuteReader()
  at PowerStatRegression.share.JbLog.SendResultSet(String str, SqlConnection conn)
  at StoredProcedures.SavePowerStatErrors(ApplicationContext app, SqlString strUID, Int32 seqId, List`1 errors, Int32 errorType)
  at StoredProcedures.CreatePowerStatCorr(SqlString strUID, Int32 seqId, Int32 flagProgress)
  at StoredProcedures.SpCreatePowerStatCorr(SqlString strUID, Int32 seqId, Int32 flagProgress)

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Data.SqlClient.SqlException: .NET Framework execution was aborted by escalation policy because of out of memory. 
System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.
System.InvalidOperationException: 
  at System.Data.SqlClient.SqlInternalConnectionSmi.ValidateConnectionForExecute(SqlCommand command)
  at System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute(String method, SqlCommand command)
  at System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async)
  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
  at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
  at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
  at System.Data.SqlClient.SqlCommand.ExecuteReader()
  at PowerStatRegression.share.JbLog.SendResultSet(String str, SqlConnection conn)
  at StoredProcedures.SavePowerStatErrors(ApplicationContext app, SqlString strUID, Int32 seqId, List`1 errors, Int32 errorType)
  at StoredProcedures.CreatePowerStatCorr(SqlString strUID, Int32 seqId, Int32 flagProgress)
  at StoredProcedures.SpCreatePowerStatCorr(SqlString strUID, Int32 seqId, Int32 flagProgress)


Source Error: 


Line 705:                    command.CommandType = CommandType.Text;
Line 706:                    command.CommandTimeout = 300;
Line 707:                    returnCode = (string)command.ExecuteScalar();
Line 708:                    //Dispose();
Line 709:                }


Source File: c:\PowerStats\datalab\powerstats\output.aspx.cs    Line: 707 

Stack Trace: 

    [SqlException (0x80131904): .NET Framework execution was aborted by escalation policy because of out of memory. 
System.InvalidOperationException: There is already an open DataReader associated with this Command which must be closed first.
System.InvalidOperationException: 
   at System.Data.SqlClient.SqlInternalConnectionSmi.ValidateConnectionForExecute(SqlCommand command)
   at System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute(String method, SqlCommand command)
   at System.Data.SqlClient.SqlCommand.ValidateCommand(String method, Boolean async)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
   at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
   at System.Data.SqlClient.SqlCommand.ExecuteReader()
   at PowerStatRegression.share.JbLog.SendResultSet(String str, SqlConnection conn)
   at StoredProcedures.SavePowerStatErrors(ApplicationContext app, SqlString strUID, Int32 seqId, List`1 errors, Int32 errorType)
   at StoredProcedures.CreatePowerStatCorr(SqlString strUID, Int32 seqId, Int32 flagProgress)
   at StoredProcedures.SpCreatePowerStatCorr(SqlString strUID, Int32 seqId, Int32 flagProgress)
]
   System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection) +1950522
   System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +4856715
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +194
   System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +1121
   System.Data.SqlClient.SqlDataReader.ConsumeMetaData() +33
   System.Data.SqlClient.SqlDataReader.get_MetaData() +83
   System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString) +293
   System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async) +954
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result) +162
   System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method) +32
   System.Data.SqlClient.SqlCommand.ExecuteScalar() +139
   Output.RunTable(String outputType, String _outputDataType) in c:\PowerStats\datalab\powerstats\output.aspx.cs:707
   Output.ProcessPage() in c:\PowerStats\datalab\powerstats\output.aspx.cs:652
   Output.Page_Load(Object sender, EventArgs e) in c:\PowerStats\datalab\powerstats\output.aspx.cs:644
   System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +14
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +35
   System.Web.UI.Control.OnLoad(EventArgs e) +99
   System.Web.UI.Control.LoadRecursive() +50
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +627




--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:2.0.50727.5456; ASP.NET Version:2.0.50727.5456 

为什么 SqlDataReader 没有被正确释放？

Answer 1

“锁定”语句是否意味着您正在多个线程中使用这些东西？
甚至不要尝试在线程之间共享 ADO .NET 对象——它们不是线程安全的……似乎有多个线程同时创建读取器实例。

Answer 2

我认为锁在错误的级别...锁需要在读者级别。释放锁后正在使用打开的阅读器。