Threading Problem

[Phreak]

I'm not completely sure on how to use threads, but I followed a small fairly simple tutorial and what I used and how I used it is below.

 

PROBLEM: Sometimes the dataset in the FillDataSet() procedure is filled (usually after you run it a second time, usually doesn't ever work the 1st time), and sometimes it doesn't. But I receive NO error of any kind. Maybe I'm not using threads correctly. Could anyone give me some input or a better way to use threads?

 

[These two procedures are taken out of the main form.]

 

Sorry if it's a little long.

 

    Private Sub OracleConnect()
       Dim dbInfo As New loginInfo()
       Dim frmProgress As New progress()

       t = New Thread(AddressOf Me.FillDataSet)


       If frmLogin.DialogResult = DialogResult.OK Or cmdRefresh = 1 Then

           'run the next couple of IFs to handle someone pushing the REFRESH
           'button if they aren't logged in
           If frmLogin.txtUser.Text = "" Or frmLogin.txtPwd.Text = "" Or frmLogin.txtServer.Text = "" Then
               cmdRefresh = MsgBox("Unable to refresh tables because you are not currently logged on." & _
                            vbCrLf & "Would you like to logon now?", MsgBoxStyle.YesNo, "Refresh Problem")
           End If

           If cmdRefresh = 6 Then
               cmdRefresh = 0
               frmLogin.ShowDialog()
               OracleConnectString(frmLogin.txtUser.Text, frmLogin.txtPwd.Text, frmLogin.txtServer.Text)
               OracleConnect()
               Exit Sub
           ElseIf cmdRefresh = 7 Then
               cmdRefresh = 0
               Exit Sub
           End If

           frmProgress.Timer1.Start()
           t.Start()

           frmProgress.ShowDialog()
           frmProgress.Timer1.Stop()

           'clear combobox items
           cmbTables.Items.Clear()
           'cmbTables.Items.Add("--None Selected--")

           'clear datagrid
           dsSeedList.Clear()
           dsSeedList.Reset()
           DataSet21.Clear()
           DataGrid1.Refresh()
           OleDbConnection1.Close()

           frmProgress.Timer1.Start()
           t.Start()

           frmProgress.ShowDialog()
           frmProgress.Timer1.Stop()

           intTblCnt = DataSet21.USER_TABLES.Rows.Count
           cmbTables.DropDownStyle = ComboBoxStyle.DropDownList

           'put avail tables into listbox (combobox)
           For i = 0 To intTblCnt - 1 Step 1
               cmbTables.Items.Add(DataSet21.USER_TABLES.Rows.Item(i).Item(0))
           Next

           If cmbTables.Items.Count > 0 Then
               cmbTables.SelectedItem = cmbTables.Items.Item(0)
           End If

           If connError = 1 Then
               connError = 0
               connError = CType(MsgBox("There was an error while trying to connect to the database." & _
                           "  Would you like to try again?", MsgBoxStyle.YesNo, "Retry Connection?"), Short)
               If connError <> 6 Then
                   connError = 0
               Else
                   frmLogin.ShowDialog()
                   If frmLogin.DialogResult = DialogResult.Cancel Then
                       Exit Sub
                   Else
                       With dbInfo
                           .user = frmLogin.txtUser.Text
                           .pass = frmLogin.txtPwd.Text
                           .serv = frmLogin.txtServer.Text
                       End With

                       Call OracleConnectString(dbInfo.user, dbInfo.pass, dbInfo.serv)
                       Call OracleConnect()
                       ButtonPressed = False
                   End If
               End If
           End If
       End If
       cmdRefresh = 0
       connError = 0
       t.Abort()
       Call CheckForTables()
   End Sub
#End Region

#Region "Fill Table Listing"
   Private Sub FillDataSet()

       Try

           'fill the dataset with the list of tables
           OleDbDataAdapter2.Fill(DataSet21, "USER_TABLES")

       Catch ex As System.Exception

           'in case an exception is thrown, give an error box and
           'a moderate description of where the exception was thrown
           If ex.GetType.ToString = "System.Threading.ThreadAbortException" Then
               'do nothing... just ignore it.  it's dumb and has no idea what it's doing.
           Else
               MsgBox("Error retrieving tables!" & vbCrLf & "Details:" & vbCrLf & "    " & _
                       ex.GetType.ToString & vbCrLf & vbCrLf & "Check your username and password " & _
                       "and make sure they are correct.", MsgBoxStyle.Critical, "Table Retrieval Error")
               connError = 1
           End If
       Finally
           OleDbConnection1.Close()
       End Try
   End Sub
#End Region

[Robby]

The way you have it now, it is stateless, you aren't getting any feedback on the thread. You will need to check on the ThreadState.

And the t.Abort() is miss-placed.

[Phreak]

What do you mean ThreadState? What state am I looking for? And if the t.Abort() is misplaced, where should it go? Like I said, I'm not familiar with using threads at all. I just need to use them in this particular occassion because of the time it takes to fill the dataset. Thanks for the reply.

[Robby]

I have only worked on Stateless (asynchronous) threading, but as a guess I would try something like this...

'this is untested ( let me know if it works)

frmProgress.ShowDialog() 
Do While t.ThreadState = ThreadState.Running

Loop
frmProgress.Timer1.Stop()

and t.Abort() should be used to abort the thread if there is an exception

[Phreak]

Yes, it does work. So far I haven't had any problems whatsoever. So hopefully this will continue to work and I won't have any more problems. Thanks a ton.