我有一个承包商在我们执行sql查询时编写了这样的代码：
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（它有大量的SQL用于统计）并在两个不同的浏览器中运行相同类型的东西，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();
}
堆栈的结果是：
.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没有正确解除分配？
答案 0 :(得分：1)
“锁定”语句是否意味着你从多个线程中使用这些东西？ 甚至不尝试在线程之间共享ADO .NET对象 - 它们不是线程安全的......似乎不止一个线程同时创建了读取器实例。
答案 1 :(得分：0)
我认为锁定处于错误的水平......锁定需要处于读者级别。锁定释放后正在使用打开的阅读器。