Popup V2 crashes on app close in an app using Shell and the TitleBar view

[RyanCathcart]

What is happening:
I created a fresh MAUI project using the VS 2022 .NET MAUI App template. This template by default uses Shell, which I feel may be important. My intention is to have the application work on Windows 10/11, so I want to be able to customize the app window's titlebar. I discovered that .NET MAUI provides a view called TitleBar, which can be used to display an icon and more. I was confused how to implement this in a MAUI app which utilizes Shell, but I was able to replicate what was done in the TitleBarDemo project provided by the dotnet/maui-samples GitHub repo, as seen here.

In essence, it uses a class called MainWindow, which inherits from the standard Microsoft.Maui.Controls.Window class. The purpose of this MainWindow class is to set the AppShell as the Window's Page property and give easy access to the TitleBar property. Here's the XAML:

Now that you have context into the setup of the project, here is the part that is actually relevant to the MAUI Community Toolkit:

I repurposed the button that came with the default MAUI app template to open a Popup via a Command, following along with much of the guide provided by the PopupService MAUI Docs.

The problem is that if at any point during the life of the app the user opens that Popup, upon closing the app, it throws an exception:

The Locals tab after the exception while debugging looks like this:

This issue only started happening after I added the TitleBar/MainWindow setup into the app. Is there anything I can do to prevent the exception from occurring? I have a more complex app that has an identical setup that uses Shell and TitleBar that I am trying to add Popups into and I created a fresh MAUI app to try to identify which part(s) of the app are causing the crashes. Any discussion or help is appreciated.

I've uploaded a repo with the code in question here:
https://github.com/RyanCathcart/MauiPopupTest

[bijington]

What happens if you replace the popup display code with just showing a ContentPage modally? Do you see the same error?

[RyanCathcart]

Thanks for the reply,
I'm not sure what you mean exactly. I'm no expert on MAUI, but from what I could tell, NavigationPage isn't compatible with Shell apps, which from my understanding was the MAUI prescribed way to display content modally. If you have any guidance, I'm eager to try new things.

EDIT: UPDATE
I created a new ContentPage and set its Shell.PresentationMode to Modal and included a similar button to navigate back to the MainPage. I am getting the same exact behavior as described in the original post. If I navigate to the modal at any point while the app is running, it throws the same exact exception upon closing the app. Perhaps this means that my issue is not with MAUI Community Toolkit?

If you have any resources or insight to offer about why this could be happening, it would be greatly appreciated!

[bijington]

You can do this with Shell and in fact it is how Popups work internally. You can use Shell.PresentationMode.

So to do this in your app you could just add a second ContentPage set Shell.PresentationMode="Modal" and then change your DisplayPopup method to something like:

[RelayCommand]
    public async Task DisplayPopup()
    {
        var queryAttributes = new Dictionary<string, object>
        {
            { nameof(ActionPopupViewModel.Message), "This is a test message for the test Popup" }
        };

        await Shell.Current.GoToAsync("routeToPage", shellParameters: queryAttributes); 
    }

[RyanCathcart]

Unfortunately using the method you described results in the same exception being thrown. However, I created a small service which manages the Microsoft.Maui.Controls.Page.DisplayAlert method, and that seems to work without throwing exceptions.

I do prefer the look of the MAUI Community Toolkit Popups, but for now I have something that is adequate. I will have to look more in depth into .NET MAUI Shell, the Community Toolkit, and how it all interacts with WinUI to figure out the issue.

[bijington]

The fact that it reproduces the issue is a good thing. Well certainly for the toolkit because it looks like a MAUI issue. It would be worth raising a bug with that team unless @jfversluis knows of anything around this area?