Object reference not set to an instance of an object.

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October 21st, 2009, 07:03 AM

pts69

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Join Date: Jun 2004

Posts: 57

Time spent in forums: 18 h 27 m 52 sec
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Object reference not set to an instance of an object.

I have written a custom namespace for my data access, the code behind and main aspx pages call a function within my namespace to retrieve some data for example:

ASPX Page:
<%=GetStringResource("SEOSiteTitle", Session("User_Locale")) %>

The session var holds "en-GB" for this example

The GetStringResource function looks like this:

Code:

        Public Shared Function GetStringResource(ByVal ResourceName As String, ByVal Locale As String) As String
            If Not String.IsNullOrEmpty(Locale) Then
                Try
                    Dim dt As New DataTable("Table")
                    dt = InlineQuerySQL("Select ConfigValue from Stringresource where Name = '" & ResourceName & "' AND LocaleSetting = '" & Locale & "'")
                    If dt.Rows.Count > 0 Then
                        Return (dt.Rows(0).Item("ConfigValue").ToString)
                    Else
                        Return ""
                    End If
                    dt.Dispose()
                Catch ex As Exception
                    Return (ex.Message.ToString)
                End Try
            Else
                Return "Please supply a locale"
            End If
        End Function

This function then calls another function to perform the actual SQL

Code:

Public Shared Function InlineQuerySQL(ByVal strSQL As String) As DataTable
            Try
                Dim SQLConn As New SqlConnection(strConnection)
                Dim sqlCommand As New SqlCommand
                With sqlCommand
                    .CommandText = strSQL
                    .Connection = SQLConn
                    .CommandType = CommandType.Text
                    .Connection.Open()
                    .ExecuteNonQuery()
                    Dim dataAdapter As New SqlDataAdapter(sqlCommand)
                    Dim dt As New DataTable()
                    dataAdapter.Fill(dt)
                    Return dt
                    .Connection.Close()
                    .Dispose()
                    dt.Dispose()
                    dataAdapter.Dispose()
                End With
                SQLConn.Close()
                SQLConn.Dispose()
            Catch ex As Exception
                Return Nothing
                'Response.Write(ex.ToString)
            End Try
        End Function

The problem I have is that I keep getting a intermittent error - " Object reference not set to an instance of an object "

This error occur on line "If dt.Rows.Count > 0 Then" of the GetStringResource function.

Does anyone have any ideas why I get this intermittent error.

Thanks

Paul

Last edited by pts69 : October 21st, 2009 at 08:03 AM.

October 21st, 2009, 09:27 AM

rclark

I do .NET for a living

Join Date: Sep 2003

Location: Florida

Posts: 1,446

Time spent in forums: 1 Week 2 Days 23 h 38 m 21 sec
Reputation Power: 182

If the try in your InlineQuerySQL function fails, your function returns Nothing (which sets the DataTable DT to nothing in the calling function GetStringResource. You can either return an empty datatable instead or test for DT = Nothing in the calling function before testing for number of rows returned.

ie: If Not DT is Nothing Then
'Test for number of rows returned

__________________
Roger (.NET MCP)

October 21st, 2009, 09:51 AM

pts69

Contributing User

Join Date: Jun 2004

Posts: 57

Time spent in forums: 18 h 27 m 52 sec
Reputation Power: 8

Thanks for that, I've managed to track the issue down to the InlineQuerySQL function sometimes returning a datatable and sometimes not.

Each time it's performing the same query so still not sure why it's erroring.

Paul

October 21st, 2009, 10:00 AM

rclark

I do .NET for a living

Join Date: Sep 2003

Location: Florida

Posts: 1,446

Time spent in forums: 1 Week 2 Days 23 h 38 m 21 sec
Reputation Power: 182

Put your response.write before the return statement and make it Response.Write(ex.Message).

October 21st, 2009, 10:22 AM

pts69

Contributing User

Join Date: Jun 2004

Posts: 57

Time spent in forums: 18 h 27 m 52 sec
Reputation Power: 8

I think we're getting somewhere now, I couldn't use response.write in namespace, so outputted the exception to a text file.

The actual error I am getting is:

Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached.

Thanks

Paul

October 21st, 2009, 10:24 AM

rclark

I do .NET for a living

Join Date: Sep 2003

Location: Florida

Posts: 1,446

Time spent in forums: 1 Week 2 Days 23 h 38 m 21 sec
Reputation Power: 182

What does your connection string look like?

October 22nd, 2009, 07:09 AM

rclark

I do .NET for a living

Join Date: Sep 2003

Location: Florida

Posts: 1,446

Time spent in forums: 1 Week 2 Days 23 h 38 m 21 sec
Reputation Power: 182

I see you're returning the datatable before closing and disposing of your connection. Try this:

Code:

Public Shared Function InlineQuerySQL(ByVal strSQL As String) As DataTable
            Try
                Dim SQLConn As New SqlConnection(strConnection)
                Dim sqlCommand As New SqlCommand
                With sqlCommand
                    .CommandText = strSQL
                    .Connection = SQLConn
                    .CommandType = CommandType.Text
                    .Connection.Open()
                    .ExecuteNonQuery()
                    Dim dataAdapter As New SqlDataAdapter(sqlCommand)
                    Dim dt As New DataTable()
                    dataAdapter.Fill(dt)
                    .Connection.Close()
                    .Dispose()
                    dt.Dispose()
                    dataAdapter.Dispose()
                End With
                SQLConn.Close()
                SQLConn.Dispose()
                Return dt          'return datatable after cleanup 
            Catch ex As Exception
                Return Nothing
                'Response.Write(ex.ToString)
            End Try
        End Function

October 22nd, 2009, 08:06 AM

pts69

Contributing User

Join Date: Jun 2004

Posts: 57

Time spent in forums: 18 h 27 m 52 sec
Reputation Power: 8

Thanks for all the help.

I've managed to get this sorted by doing the following:

Code:

Dim SQLConn
Dim SQLCommand

Try
   Do my Stuff
Catch
   Catch and Log the exception
Finally
   Dispose of SQLConn
   Dispose of SQLCommand
End Try

By adding the finally, I can make sure that all connections are close whether try passes or fails.

Thanks all

Paul

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