Application.LoadComponent makes application freeze on shutdown

Question

If I use Application.LoadComponent() to load a UserControl, Page or Window, my application freezes when I try to close it.

The app apparently closes, but the process keeps running. Easy to notice when debugging.

I've tested it under Windows 7 64bit and Vista 32bit. In both cases I have used VS2008 and .NET 3.5.

A repro can be built by creating a wpf application as follows:

    public partial class Window1 : Window {
        public Window1() {
            InitializeComponent();
        }
        public void LoadCopy() {
            var uri = new Uri("/WpfApplication1;component/window1.xaml", UriKind.Relative);
            var copy = (Window)Application.LoadComponent(uri);
            MessageBox.Show(copy.Title);
        }
        private void Button_Click(object sender, EventArgs e) {
            LoadCopy();
        }
    }

Does anyone know what might be happening? And how to solve it?

Answer 1

I have build you application on Windows 7 32bit under .Net 4.0 and 3.5. I works fine for me. I think you problem is configuration specific. Which configuration do you have? Do you reference any assemblies except default WPF project references?

Answer 2

Try assigning the owner to the created assembly i.e. copy.Owner = this;

I was able to close your example after doing this.

Answer 3

I think it is because you are calling LoadComponent() on what is also your Main Window ( http://msdn.microsoft.com/en-us/library/system.windows.application.mainwindow.aspx ), i.e. the startup uri, in your case Window1. The program is probably entering some loop when you close it because closing a Main Window by default shuts down the Application and your two instances of Window1 are waiting on each other (A.K.A. a deadlock)! Albeit seemingly only after making the Application invisible (so it seems to have closed).

If you still must use use LoadComponent() on Window1 I think you would need to not make it your startup uri by changing the StartupUri of your Application:

<Application
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 StartupUri="Window1.xaml"> <!-- change this -->
</Application>

Or change Application.ShutdownMode ( http://msdn.microsoft.com/en-us/library/system.windows.application.shutdownmode.aspx ) to OnLastWindowClose:

<Application
 xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
 xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 StartupUri="Window1.xaml"
 ShutdownMode="OnLastWindowClose">
</Application>