使用BackGroundWorker的错误处理条件失败

Question

To get used to and get trained using Backgroundworker for my Project, i used a sample code which runs smoothly except when it comes to handling error condition it doesn't allow me to use (e.Error!=null) facility of RunWorkerCompletedEventArgs e .I want to handle error like the way cancel and successful completion works for me.

Suggestions please! Following is the code:

      private void DoWork(object sender, DoWorkEventArgs e)
        {
           Random rand = new Random();
           for (int i = 0; i < 10; i++)
             {
                 if (this.backgroundWorker.CancellationPending)
                  {
                     e.Cancel = true;
                     break;

                  }

                 // report progress
                 this.backgroundWorker.ReportProgress(-1, string.Format("Performing step {0}...", i + 1));

                 // simulate operation step
                System.Threading.Thread.Sleep(rand.Next(1000, 10000));

                //setting simulateError to true after inducing error(a button)
                if (this.simulateError)
                  {
                    this.simulateError = false;
                    //needs a code to use (e.Error!=null) in 
                      RunWorkerCompleted().
                   //A jump to RunWorkerCompleted is required here.

                  }



           }
      }
    private void RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        // hide animation
         this.pictureBox.Image = null;

        // show result indication
        if (e.Cancelled)
        {   
            ////works nice 
            this.labelProgress.Text = "Operation cancelled by the user!";
            this.pictureBox.Image = Properties.Resources.WarningImage;
        }
        else
        {
           //doesn't execute at all....why?

            if (e.Error != null)
            {
                this.labelProgress.Text = "Operation failed: " + e.Error.Message;
                this.pictureBox.Image = Properties.Resources.ErrorImage;
            }
            else
            {
                //works nice
                this.labelProgress.Text = "Operation finished successfuly!";
                this.pictureBox.Image = Properties.Resources.InformationImage;
            }
        }

        // restore button states
        this.buttonStart.Enabled = true;
        this.buttonCancel.Enabled = false;
        this.buttonError.Enabled = false;
    }

I induce error using simulateError ,for the purpose to show peculiar error message how should i use

   if (e.Error != null)
            {
                this.labelProgress.Text = "Operation failed: " +  e.Error.Message;

My Program isn't coming to private void RunWorkerCompleted(object sender, ,RunWorkerCompletedEventArgs e) in case of error. In other cases(cancellation,succesful completion) it executes right.

Answer 1

To get used to and get trained using Backgroundworker for my Project

Why would you do that? Task.Run() is better than BackgroundWorker in every way.

---

Now to your actual question: to cause an error in a BackgroundWorker , use the standard mechanism for that in .Net: exceptions:

if (this.simulateError)
{
    this.simulateError = false;

    throw new Exception("Simulating error.");
}