Shutting down a WPF application from App.xaml.cs

Question

I am currently writing a WPF application which does command-line argument handling in App.xaml.cs (which is necessary because the Startup event seems to be the recommended way of getting at those arguments). Based on the arguments I want to exit the program at that point already which, as far as I know, should be done in WPF with Application.Current.Shutdown() or in this case (as I am in the current application object) probably also just this.Shutdown() .

The only problem is that this doesn't seem to work right. I've stepped through with the debugger and code after the Shutdown() line still gets executed which leads to errors afterwards in the method, since I expected the application not to live that long. Also the main window (declared in the StartupUri attribute in XAML) still gets loaded.

I've checked the documentation of that method and found nothing in the remarks that tell me that I shouldn't use it during Application.Startup or Application at all.

So, what is the right way to exit the program at that point, ie the Startup event handler in an Application object?

Answer 1

First remove the StartupUri property from App.xaml and then use the following:

    protected override void OnStartup(StartupEventArgs e)
    {
        base.OnStartup(e);

        bool doShutDown = ...;

        if (doShutDown)
        {
            Shutdown(1);
            return;
        }
        else
        {
            this.StartupUri = new Uri("Window1.xaml", UriKind.Relative);
        }
    }

Answer 2

If you remove the StartupUri from app.xaml for an application with a MainWindow you need to make sure you make the following call in your OnStartup method otherwise the application will not terminate when your MainWindow closes.

this.ShutdownMode = System.Windows.ShutdownMode.OnMainWindowClose;

@Frank Schwieterman, something along these lines may help you with your console window issue.

Answer 3

I did this a little differently to avoid having to set the StartupUri and ShutdownMode properties. First edit the App.xaml file and replace StartupUri with Startup :

<Application x:Class="Menu.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:local="clr-namespace:Menu"
         Startup="Application_Startup">
    <Application.Resources>
    </Application.Resources>
</Application>

Then add Application_Startup to the code along with OnExit :

public partial class App : Application
{
    private volatile static Mutex s_mutex;

    private void Application_Startup(object sender, StartupEventArgs e)
    {
        s_mutex = new Mutex(true, @"Global\MenuMutex", out bool grantedOwnership);

        if (!grantedOwnership)
        {
            MessageBox.Show($"Another instance is already running!", "Error", MessageBoxButton.OK, MessageBoxImage.Exclamation);
            Current.Shutdown();
        }
        else
            new MainWindow().Show();
    }

    protected override void OnExit(ExitEventArgs e)
    {
        s_mutex?.ReleaseMutex();
        s_mutex?.Dispose();
        s_mutex = null;
        base.OnExit(e);
    }

Answer 4

Write in the Application_Startup:

private void Application_Startup(object sender, StartupEventArgs e)  
{  
    ...
    if (!condition)  
    {  
        e.GetType()  
          .GetProperty("PerformDefaultAction", BindingFlags.Instance | BindingFlags.NonPublic)  
          .SetValue(e, false);  
        Shutdown();  
        return;  
    }  
    ...
}