Question

So … I’ve got some static class with some method which returns some data to my Data Tables.

The trouble is multi-access to this method. When to different Client Sessions call this method in the same time DataReaded fails with error that I need to close current command (DataReader) before start new one. I even tried to use Lock but this didn’t made any sense.

    private RepGroupsDataSourcelocker = Object()
    public RepGroupsDataSource() : array[(string * int)]
        lock(RepGroupsDataSourcelocker)
            def res = linq<#from pr in _Rep_Permission
                    from rg in _Rep_Group
                    where (pr.ID_User == System.Web.HttpContext.Current.User.Identity.Name)
                    where (rg.RepGroup_ID == pr.ID_RepGroup)
                    order by rg.nOrder
                    select (rg.RepGroup_Name, rg.RepGroup_ID)
                    #>
            res.Take(7).ToArray()

That is only example code , it fails on any linq2sql , SqlAdapter Fill commands.

Here is details :

System.InvalidOperationException was unhandled by user code
      Message = There is a designated this command Command open DataReader, which requires the prior close.
      Source = System.Data
      StackTrace:
           in System.Data.SqlClient.SqlInternalConnectionTds.ValidateConnectionForExecute (SqlCommand command)
           in System.Data.SqlClient.SqlConnection.ValidateConnectionForExecute (String method, SqlCommand command)
           in System.Data.SqlClient.SqlCommand.ValidateCommand (String method, Boolean async)
           in System.Data.SqlClient.SqlCommand.RunExecuteReader (CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
           in System.Data.SqlClient.SqlCommand.RunExecuteReader (CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
           at System.Data.SqlClient.SqlCommand.ExecuteReader (CommandBehavior behavior, String method)
           in System.Data.SqlClient.SqlCommand.ExecuteDbDataReader (CommandBehavior behavior)
           in System.Data.Common.DbCommand.System.Data.IDbCommand.ExecuteReader (CommandBehavior behavior)
           in System.Data.Common.DbDataAdapter.FillInternal (DataSet dataset, DataTable [] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior)
           in System.Data.Common.DbDataAdapter.Fill (DataTable [] dataTables, Int32 startRecord, Int32 maxRecords, IDbCommand command, CommandBehavior behavior)
           in System.Data.Common.DbDataAdapter.Fill (DataTable dataTable)
           in Flow_WEB_Nemerle.SQLModule.GetReport (String Param1, Int32 Param2, Int32 Group, Int32 DayOfMonth, String ContactHour, Int32 MyCase, Boolean ForDia, Int32 step, Int32 maximumRows, Int32 startRowIndex) in D: \ SVN \ FlowServer \ trunk \ FS WEB \ Flow_WEB_Nemerle2 \ SQLReportModule.n: line 96
      InnerException:

How can I avoid this troubles without creating a Windows Service / WCF for it. I want really fast solution … Maybe I need dynamic class with methods ?

Answer 1

The web server uses several threads for handling requests. If they all use the same database connection, that is a bottle neck for the site.

You should use a separate database connection for each request. That way there is no concurrency problems between the threads, and you don’t create an unneccesary bottle neck.