App.UnhandledException doesn't catch exceptions from other threads.

Describe the bug Unable to catch UnhandledException (at app level) when the exception originates from async Task.

Steps to reproduce the bug

1. Create new WinUI3 project
2. In App.cs handle UnhandledException:

public App()
        {
            this.InitializeComponent();
            this.UnhandledException += App_UnhandledException;
        }


        private void App_UnhandledException(object sender, Microsoft.UI.Xaml.UnhandledExceptionEventArgs e)
        {
            Debug.WriteLine("WinUI App Crashed");
        }

1. In MainWindow.cs add a button with code-behind that will throw a devide-by-zero exception from an Async method:

private async void myButton_Click(object sender, RoutedEventArgs e)
        {
            int t = await Task.Run(() =>
            {
                var x = 0;
                var y = 3 / x;
                return y;
            });
        }

Expected behavior Would expect the App_UnhandledException to ‘handle’ this exception.

Screenshots

Version Info WinUI 0.8.0-preview Windows 10

NuGet package version: Microsoft.ProjectReunion (0.8.0-preview) Microsoft.ProjectReunion.Foundation (0.8.0-preview) Microsoft.ProjectReunion.WinUI (0.8.0-preview)

Windows app type:

UWP	Win32
No	Yes

Windows 10 version	Saw the problem?
Insider Build (xxxxx)
October 2020 Update (19042)	Yes
May 2020 Update (19041)
November 2019 Update (18363)
May 2019 Update (18362)
October 2018 Update (17763)
April 2018 Update (17134)
Fall Creators Update (16299)
Creators Update (15063)

Device form factor	Saw the problem?
Desktop	Yes
Xbox
Surface Hub
IoT

Additional context GitHub example with 2 ‘identical’ projects, one UWP (WinUI2) and one WinUI3, to show the difference in behavior between the two. https://github.com/artkat/CrashingApp

[artkat]

This bug has been reported nearly a year ago. Still, no one has been assigned to fix it. I’m disappointed, frustrated, annoyed, and honestly quite pissed that this is the way Microsoft handles this project.

[Scottj1s]

App.UnhandledException fix will be available in Windows App SDK 1.2 Preview 2