C # opennetCF background worker - e.result gives an ObjectDisposedException

Question

I work with a background worker in C #. Here is a class, and under it you will find its instansiation, and there I will define my problem for you:

I have a Drawing class:

class Drawing
{
    BackgroundWorker bgWorker;
    ProgressBar progressBar;
    Panel panelHolder;

    public Drawing(ref ProgressBar pgbar, ref Panel panelBig)  // Progressbar and panelBig as reference
    {
        this.panelHolder = panelBig;
        this.progressBar = pgbar;
        bgWorker = new BackgroundWorker();
        bgWorker.WorkerReportsProgress = true;
        bgWorker.WorkerSupportsCancellation = true;

        bgWorker.DoWork += new OpenNETCF.ComponentModel.DoWorkEventHandler(this.bgWorker_DoWork);
        bgWorker.RunWorkerCompleted += new OpenNETCF.ComponentModel.RunWorkerCompletedEventHandler(this.bgWorker_RunWorkerCompleted);
        bgWorker.ProgressChanged += new OpenNETCF.ComponentModel.ProgressChangedEventHandler(this.bgWorker_ProgressChanged);
    }

    public void createDrawing()
    {
        bgWorker.RunWorkerAsync();
    }

    private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
    {
       Panel panelContainer = new Panel();

          // Adding panels to the panelContainer
          for(i=0; i<100; i++)
          {
            Panel panelSubpanel = new Panel();
            // Setting size, color, name etc....

             panelContainer.Controls.Add(panelSubpanel);  // Adding the subpanel to the panelContainer

             //Report the progress
             bgWorker.ReportProgress(0, i); // Reporting number of panels loaded
          }

          e.Result = panelContainer;   // Send the result(a panel with lots of subpanels) as an argument 
    }

    private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
          this.progressBar.Value = (int)e.UserState; 
          this.progressBar.Update();
    }

    private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if (e.Error == null)
        {
            this.panelHolder          = (Panel)e.Result; 
        }
        else
        {
            MessageBox.Show("An error occured, please try again");
        }
    }

}

The instance of this class is:

public partial class Draw: Form
{
  public Draw()
  {


      ProgressBar progressBarLoading = new ProgressBar();
      // Set lots of properties on progressBarLoading 

      Panel panelBigPanelContainer = new Panel();          

      Drawing drawer = new Drawing(ref progressBarLoading, ref panelBigPanelContainer);

      drawer.createDrawing(); // this makes the object start a new thread, loading all the panels into a panel container, while also sending the progress to this progressbar.
  }

}

Here is my problem: In private void bgWorker_RunWorkerCompleted (object sender, RunWorkerCompletedEventArgs e)

I do not get e.Result, as it should be. When I debug and look at e.Result, the panel properties have this exception message:

'((System.Windows.Forms.Control)(e.Result)).ClientSize' threw an exception of type    'System.ObjectDisposedException'

Thus, the object becomes deleted, but “why” is my question, and how can I fix it?

I hope someone answers me, it makes me go crazy. Another question I have is: is the use of ref arguments allowed? is it bad programming?

Thanks in advance.

, :

---

, "" :

bgWorker.RunWorkerAsync();   => starts a new thread.
bgWorker_DoWork cannot reach the main thread without delegates

-

private void bgWorker_DoWork(object sender, DoWorkEventArgs e)
{
       // The work happens here, this is a thread that is not reachable by 
          the main thread

       e.Result  => This is an argument which can be reached by
                    bgWorker_RunWorkerCompleted()


       bgWorker.ReportProgress(progressVar);  => Reports the progress to the
                                                 bgWorker_ProgressChanged()           

}

-

    private void bgWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
    {
           // I get the progress here, and can do stuff to the main thread from here 
              (e.g update a control)

              this.ProgressBar.Value = e.ProgressPercentage;
     }

-

    private void bgWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        // This is where the thread is completed.
        // Here i can get e.Result from the bgWorker thread
        // From here i can reach controls in my main thread, and use e.Result in my main thread


        if (e.Error == null)
        {
            this.panelTileHolder  = (Panel)e.Result;

        }
        else
        {
            MessageBox.Show("There was an error");
        }
    }

Answer 1

, "imagePanel", , - , . , , , Windows , ( Controls.Add()) , , ..NET 2.0 IllegalOperationException, , , CF. .

ObjectDisposedException BackgroundWorker RunWorkerCompleted ProgressChanged, . , BGW, . - , .

Answer 2

() . . , , , , , , -, . RunWorkerCompleted , ObjectDisposedException.

, . ProgressChanged, , , , InvokeRequired , , Invoke. , , RunWorkerCompleted .

-.

WinForms UI Thread Invokes: In-Depth Review of Invoke/BeginInvoke/InvokeRequred