How to keep ProgressBar Indeterminate animating

Question

I've been learning about how this issue is confronted via Threads ( BackgroundWorker and others) and how to keep the UI responsive. I've managed to do so but then I realized that is not what I want. What I need actually is just to display an animating ProgressBar while a long operation is performed. (I don't need/want to update the UI because in that operation I'm exporting all graphical representation and the plotter is updated constantly).

I have thought about a Dialog popping-up with the progress bar while the operation is being performed. The problem is that I get this exception:

The calling thread cannot access this object because a different thread owns it

There are plenty of questions about this and the answer is to use Dispatcher :

            Dispatcher.CurrentDispatcher.Invoke(() => myOperation(), DispatcherPriority.Normal);

Here is what've done:

I'm using Modern UI, there is a Dialog called ModernDialog, it's just a fancy dialog:

  class DialogProgress
{
    public ModernDialog progressDlg = new ModernDialog();

    public DialogProgress()
    {
        ProgressBar bar = new ProgressBar();
        bar.IsIndeterminate = true;
        bar.Width = 150;
        StackPanel content = new StackPanel();
        content.Children.Add(bar);
        progresoDlg.Content = content ;

        //Thread paralel = new Thread(() => myOperation());
        //paralel.SetApartmentState(ApartmentState.STA);
        //paralel.Start();
        Dispatcher.CurrentDispatcher.Invoke(() => myOperation(), DispatcherPriority.Normal);
    }

    void myOperation()
    {
        progresoDlg.ShowDialog();
    }
}

I know I'm mixing stuff there, there are Threads and Dispatcher, but I can't figure out how to use them.

Here is how I call this dialog:

public void MyLongMethod()
{
        DialogProgress progress = new DialogProgress();
}

If I use only Dispatcher, the dialog shows up and the bar is being animated but MyLongMethod is not working (it starts after closing the dialog).

If I use Threads I get the mentioned exception.

How can I solve this problem?

(PD using a dialog Is only a suggestion, I would be happy too if the progress bar is in the UI and I switch the visibility when the long method starts/ends)

Answer 1

    Dispatcher.CurrentDispatcher.Invoke(...);

This goes wrong because you used Invoke(), it will not return until the invoked method finished running. Which will take a while, ShowDialog() is a blocking call that doesn't complete until the user closes the dialog.

The simple workaround is to use BeginInvoke() instead.

Answer 2

Assuming ModernDialog is a WPF Window , the ShowDialog method does not return until it's closed. Invoke also doesn't return until the operation is called and returns. You need to either use Show instead of ShowDialog , or call it with BeginInvoke instead of Invoke . I would use Show , because ShowDialog doesn't really make sense unless you are waiting for the user to respond by clicking a dialog button.