.Net BackgroundWorker Component

Overview

• Is a helper class in System.ComponentModel namespace
• Manages a worker thread
• Handles automatic marshaling/invoking: can update Windows forms

Use BackgroundWorder

• Add a BackgroundWorker component to the form.
• Run it:

  backgroundWorker1.RunWorkerAsync();
  // Parameter can be pass to worker as well
  backgroundWorker1.RunWorkerAsync(Object param);

• Implement actual work in the DoWork event:

  private void backgroundWorker1_DoWork(
  object sender, DoWorkEventArgs e){ 
  // long task... 
  }

• Cleanup when done:

  private void backgroundWorker1_RunWorkerCompleted(
  object sender, RunWorkerCompletedEventArgs e){ 
  // Clean up... 
  }

To be able to cancle background work

• Enable worker cancellation support:

  backgroundWorker1
    .WorkerSupportsCancellation = true;

• Cancel worker:

  backgroundWorker1.CancelAsync();

• Check cancel event in DoWork event

  private void backgroundWorker1_DoWork(
  object sender, DoWorkEventArgs e){ 
    // long task... 
    BackgroundWorker worker= (BackgroundWorker)sender;
    If (worker.CancellationPending == true) {
      e.Cancel = True
      // Cancel long task
    }
  }

• Check cancel event in RunWorkerCompleted event

  private void backgroundWorker1_RunWorkerCompleted(
  object sender, RunWorkerCompletedEventArgs e){ 
    // Clean up... 
    if (e.Cancelled){
      MessageBox.Show("Cancelled");
    }
  }

If need to report progress

• Enable backgrounWorker progress report:

  backgroundWorker1.WorkerReportsProgress = true;

• Add a ProgressBar component to the form
• Update progress bar in ProgressChanged event:

  private void backgroundWorker1_ProgressChanged(
  object sender, ProgressChangedEventArgs e){
    BackgroundWorker worker = 
      (BackgroundWorker)sender;
    worker.ReportProgress(10);
  }

Reference:

• Understanding the BackgroundWorker Component