How to stop BackgroundWorker on Form's Closing event?

Question

I have a form that spawns a BackgroundWorker, that should update form's own textbox (on main thread), hence Invoke((Action) (...)); call.
If in HandleClosingEvent I just do bgWorker.CancelAsync() then I get ObjectDisposedException on Invoke(...) call, understandably. But if I sit in HandleClosingEvent and wait for bgWorker to be done, than .Invoke(...) never returns, also understandably.

Any ideas how do I close this app without getting the exception, or the deadlock?

Following are 3 relevant methods of the simple Form1 class:

    public Form1() {         InitializeComponent();         Closing += HandleClosingEvent;         this.bgWorker.RunWorkerAsync();     }      private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) {         while (!this.bgWorker.CancellationPending) {             Invoke((Action) (() => { this.textBox1.Text = Environment.TickCount.ToString(); }));         }     }      private void HandleClosingEvent(object sender, CancelEventArgs e) {         this.bgWorker.CancelAsync();         /////// while (this.bgWorker.CancellationPending) {} // deadlock     } 

Answer 1

The only deadlock-safe and exception-safe way to do this that I know is to actually cancel the FormClosing event. Set e.Cancel = true if the BGW is still running and set a flag to indicate that the user requested a close. Then check that flag in the BGW's RunWorkerCompleted event handler and call Close() if it is set.

private bool closePending;  protected override void OnFormClosing(FormClosingEventArgs e) {     if (backgroundWorker1.IsBusy) {         closePending = true;         backgroundWorker1.CancelAsync();         e.Cancel = true;         this.Enabled = false;   // or this.Hide()         return;     }     base.OnFormClosing(e); }  void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) {     if (closePending) this.Close();     closePending = false;     // etc... } 

Answer 2

I've found another way. If you have more backgroundWorkers you can make:

List<Thread> bgWorkersThreads  = new List<Thread>(); 

and in every backgroundWorker's DoWork method make:

bgWorkesThreads.Add(Thread.CurrentThread); 

Arter that you can use:

foreach (Thread thread in this.bgWorkersThreads)  {      thread.Abort();     } 

I used this in Word Add-in in Control, which i use in CustomTaskPane. If someone close the document or application earlier then all my backgroundWorkes finishes their work, it raises some COM Exception(I don't remember exatly which).CancelAsync() doesn't work.

But with this, I can close all threads which are used by backgroundworkers Immediately in DocumentBeforeClose event and my problem is solved.