How to display a dialog when the application is closing?

[harvinders]

I am trying to display a dialog to confirm if the user would like to save their work before the application is closed, but it does not seem to be working, either the application crashes or it hangs.

I am trying to subscribe to the AppWindow.Closing event and display a content dialog using ContentDialog.ShowAsync().

• ContentDialog.ShowAsync().GetAwaiter().GetResult() cause Unhandled exception.
• I can also not see any Deferral documentation that could help pause the app close whilst I display the dialog.

I suppose this a very basic ask. Am I missing something or WinUI3/WinAppSDK missing this feature too?

[jp-weber]

In the AppWindow.Closing event, I would interrupt the closing e.Handled = true and then open the dialog in another task. In the dialog task, I would suggest setting a boolean or an enum at this point for a status whether the user confirms the closing. if this is confirmed, the status must be set and the application closed via the exit command. In this case, of course, AppWindow.Closing is called up again, in which case the closing of the application must not be prevented on the basis of the status.

I have implemented something similar in an application that interacts with a trayicon.

[castorix]

This works for me (Windows 10 22H2, Windows app SDK 1.1.0) :

    private async void AppW_Closing(Microsoft.UI.Windowing.AppWindow sender, Microsoft.UI.Windowing.AppWindowClosingEventArgs args)
    {
        args.Cancel = true;

        ContentDialog cd = new ContentDialog
        {
            Title = "Question",
            Content = "Do you want to quit ?",
            PrimaryButtonText = "Yes",
            SecondaryButtonText = "No"
        };
        cd.XamlRoot = this.Content.XamlRoot;
        var cdResult = await cd.ShowAsync();
        if (cdResult == ContentDialogResult.Primary)
        {
            this.Close();
        }
    }

[gluetheknot2]

WHERE DO I ADD THIS????!!!!!

[DarranRowe]

The MainWindow class.
This is the only place where you can obtain the AppWindow to subscribe to the Closing event, which the answer is the handler for. This is the only place where you can also use the Content property to obtain the XamlRoot from.