My WPF app still running if I open another Window

Question

Hello, I'm writting an WPF application using the mvvm toolkint.

In the main windows I have a command in a button that open another window using:

catView.ShowDialog();

Well, I close that window (using a close button or the X) and when I close the main window, the app is still running and I have to kill it.

If I don't open the second window, the app shutdown normally.

Why if I open another window I can't close the app normally?

I have this in the close button of the second window:

this.DialogResult = true;
this.Close();

On the other hand, I start the app in this way (mvvm toolkit way):

Views.MainView view = new Views.MainView();
view.DataContext = new ViewModels.MainViewModel();
view.Show();

Thank you very much.

Answer 1

I don't know if this is causing your issue or not, but you don't need the call to Close() in your second window. Setting the DialogResult automatically closes the window.

Answer 2

The problem is probably unrelated to opening and closing the window but is somthing inside that window.

This usually happens when you have another thread still running when you close the application, check for anything that might be creating a new thread inside the window's code (including System.Threading.Thread, ThreadPool, BackgroundWorker and 3rd party components), make sure all background threads shut down before closing the application (or if you can't shut them down at least mark them as background threads).

Also look for anything that can open another (invisible) window, it's common to use window messages to an invisible window as an inter-process communication mechanism, again look for 3rd party code that might be doing that.

Answer 3

Nir is correct, a thread is probably still running in your other window.

You can fix this by terminating the application's thread dispatcher when the window closes.

public Window1()
{
    InitializeComponent();

    // This line should fix it:
    this.Closed += (sender, e) => this.Dispatcher.InvokeShutdown();
}

I'm happy to be corrected if this is not the right way to do things. Worked well for me though.

PS. If your other window is designed to run in a different thread, then read this by Eugene Prystupa: running-wpf-application-with-multiple-ui-threads