Question

I am looking to build a multi-threaded text import facility (generally CSV into SQL Server 2005) and would like to do this in VB.NET but I am not against C#. I have VS 2008 trial and just dont know where to begin. Can anyone point me in the direction of where I can look at and play with the source of a VERY simple multi-threaded application for VS 2008?

Thanks!

Answer 1

The referenced DevX article is from 2001 and .Net Framework 1.1, but today .Net Framework 2.0 provides the BackgroundWorker class. This is the recommended threading class if your application includes a foreground UI component.

From MSDN Threads and Threading:

If you need to run background threads that interact with the user interface, the .NET Framework version 2.0 provides a BackgroundWorker component that communicates using events, with cross-thread marshaling to the user-interface thread.

This example from MSDN BackgroundWorker Class shows a background task, progress %, and cancel option. (The example is longer than the DevX sample, but has a lot more functionality.)

Imports System.ComponentModel  Partial Public Class Page     Inherits UserControl     Private bw As BackgroundWorker = New BackgroundWorker      Public Sub New()         InitializeComponent()          bw.WorkerReportsProgress = True         bw.WorkerSupportsCancellation = True         AddHandler bw.DoWork, AddressOf bw_DoWork         AddHandler bw.ProgressChanged, AddressOf bw_ProgressChanged         AddHandler bw.RunWorkerCompleted, AddressOf bw_RunWorkerCompleted      End Sub     Private Sub buttonStart_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs)         If Not bw.IsBusy = True Then             bw.RunWorkerAsync()         End If     End Sub     Private Sub buttonCancel_Click(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs)         If bw.WorkerSupportsCancellation = True Then             bw.CancelAsync()         End If     End Sub     Private Sub bw_DoWork(ByVal sender As Object, ByVal e As DoWorkEventArgs)         Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)          For i = 1 To 10             If bw.CancellationPending = True Then                 e.Cancel = True                 Exit For             Else                 ' Perform a time consuming operation and report progress.                 System.Threading.Thread.Sleep(500)                 bw.ReportProgress(i * 10)             End If         Next     End Sub     Private Sub bw_RunWorkerCompleted(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs)         If e.Cancelled = True Then             Me.tbProgress.Text = 'Canceled!'         ElseIf e.Error IsNot Nothing Then             Me.tbProgress.Text = 'Error: ' & e.Error.Message         Else             Me.tbProgress.Text = 'Done!'         End If     End Sub     Private Sub bw_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs)         Me.tbProgress.Text = e.ProgressPercentage.ToString() & '%'     End Sub End Class