VB.NET - Background worker - Asked By Ben Sebuabe on 29-Jan-14 12:08 PM

I am using vb.net 2008 which is connected to sql 2008. I have a timer control and a tooltip. The timer always keeps on ticking and when a condition is met the tooltip displays a message. My problem now is the timer hangs or freezes the program.

I thought of a Background worker that works on a separate thread, but how to go about it.

How can I put the IterateMovement procedure below in a background worker? Thanks



Private Sub TimerIterate_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TimerIterate.Tick

      Call IterateMovement()

    End Sub





Public Sub IterateMovement()

Dim SQLCon As SqlConnection

Dim dtDays As New DataSet

strUsername = GetSetting("Lands", "Connection", "DataL1")

strPassword = GetSetting("Lands", "Connection", "DataL2")

strServerName = GetSetting("Lands", "Connection", "DataL3")

strInitialCatalog = GetSetting("Lands", "Connection", "DataL4")

DataL1 = strUsername & strPassword & " Connect Timeout=0; " & strServerName & strInitialCatalog

SQLCon = New SqlConnection

daAdapter = New SqlDataAdapter

dtDays = New DataSet

SQLCon.ConnectionString = DataL1

'Weekly Files to be received

Dim Query As String = "Select * from File_Movement where Movement_to ='" & frmVisibleNot.txtUsername.Text.Trim & "' and Received_By is null and fdate >  dateadd(day,-7, getdate()) order by Fdate desc,Ftime desc"

daAdapter.SelectCommand = New SqlCommand(Query, SQLCon)

Try

SQLCon.Open()

daAdapter.Fill(dtDays, "File_movement").ToString.Trim()

Dim table As DataTable = dtDays.Tables("File_movement")

If table.Rows.Count > 0 Then

frmHome.ToolTip1.Show("YOU HAVE FILE(S) TO RECEIVE, CLICK ON THE BUTTON TO SEE THEM", frmHome.btnMessage, 10000)

frmHome.ToolTip1.ToolTipTitle = "Lands Messenger"

frmHome.ToolTip1.UseAnimation = True

frmHome.btnMessage.Visible = True

frmHome.ToolTip1.BackColor = Color.Red

frmHome.ToolTip1.ForeColor = Color.White

Else

frmHome.ToolTip1.Hide(frmHome.btnMessage)

frmHome.btnMessage.Visible = False

End If

daAdapter.Dispose()

dtDays.Dispose()

SQLCon.Dispose()

daAdapter = Nothing

SQLCon.Close()

SQLCon = Nothing

Catch

End Try

End Sub

#End Region

Robbe Morris replied to Ben Sebuabe on 29-Jan-14 12:46 PM

In your case, I don't think it needs to be that complex. Create a class level bool variable called _inProgress

At the beginning of IterateMovement, set this variable to true. In the finally clause of IterateMovement (you'll need to add that after your Catch statement), set _inProgress = false

In the TimerIterate_Tick event, check to see if _inProgress = true. If so, don't call IterateMovement and exit the sub.

My guess is that your stuff is getting hung up because you are setting the Timer to tick every few milliseconds and then calling IterateMovement again and again before it had a chance to complete. This simple arrangement will let you constantly check every few milliseconds but not execute again until the previous IterateMovement has finished.