Why BackgroundWorker always is busy?

Question

I realized something strange in my background worker in my WPF application.

What I'm trying to accomplish right now is to wait until the BW finishes to start another thread.

Check the following code:

if (bw.IsBusy)
{
    bw.CancelAsync();

    System.Threading.ThreadStart WaitThread = 
        new System.Threading.ThreadStart(delegate() {
            while (bw.IsBusy)
            {
                System.Threading.Thread.Sleep(100);
            }

            bw.RunWorkerAsync();
        });

    System.Windows.Application.Current.Dispatcher.Invoke(
        System.Windows.Threading.DispatcherPriority.Normal,
        WaitThread);  // if I remove this line, bw fires RunWorkerAsyncEvent
}
else
{
    bw.RunWorkerAsync();
}

Please note that I added a Dispatcher.Invoke to wait until the bw is not busy, but ALL THE TIME IS BUSY if I Invoke it and never fires the RunWorkerAsyncCompleted event. Although,, if I remove that line, FIRES the event and it's really strange that.

How can I wait until the bw finishes?

Answer 1

The deadlock occurs due to the "main" thread of the application can not run (and handle events), thus the Backgroundworker is never able to fire it's finished-function. What you can do to allow the application to fire this is add an Application.DoEvents();

This is what I currently use in a similiar scenario, and it appears to work like a charm!

    while (bw.IsBusy)
    {
        Application.DoEvents();
        System.Threading.Thread.Sleep(100);
    }