Run WPF window in separate thread and await for it to close

I need to run a new WPF window in parallel with the main one on button click. Another window should not open until the previous was closed. I found this answer to run a new window in separate thread and this answer to await the Closed event.

I tried to combine them using Task but encountered the following problem. A new window opens independently from the main one, but await task does not pause the function execution. In addition, when I close the main window, a new window remains.

Can anyone suggest me how to solve the problem?

bool signal = false; 

private async void butHelp1_Click(object sender, RoutedEventArgs e)
{
    // Check the global signal variable to not let a new window open
    if (signal) return;

    signal = true;

    Task task = Task.Run(() =>
    {
        Thread thread = new(() =>
        {
            NewWindow window = new();
            window.ShowDialog();

            System.Windows.Threading.Dispatcher.Run();
        });

        thread.SetApartmentState(ApartmentState.STA);
        thread.Start();
    });

    // This line does not pause the function execution
    await task;

    signal = false;
}

>Solution :

If I understand correctly what you need, then look at this implementation:

        private bool isClosedNewWindow = false;
        private NewWindow? newWindow;

        private void butHelp1_Click(object sender, RoutedEventArgs e)
        {
            if (isClosedNewWindow)
            {
                if (newWindow?.WindowState == WindowState.Minimized)
                    newWindow.WindowState = WindowState.Normal;
            }
            else
            {
                isClosedNewWindow = true;

                newWindow = new NewWindow();
                newWindow.Closed += delegate { isClosedNewWindow = false; };
                newWindow.Show();
            }
        }