App crashes while starting if entrypoint set to <projectname>.App in Package.appxmanifest

[EP012014]

Describe the bug

If you set entrypoint to the App class to make the app a CoreWindow Application, the app will crash during the splash screen.

Steps to reproduce the bug

1.Go to Package.appxmanifest and set the Entrypoint to .App
2.Disable the default generated Main method by defining DISABLE_XAML_GENERATED_MAIN and copy the auto-generated code in App.g.i.cs to Program.cs. Remove the [global::System.STAThreadAttribute] attribute to avoid thread-related issues due to different threading model used by CoreApplication and Legacy Desktop Application.
3.Run the app in debug mode.
The app will crash before InitializeComponent with an exception in Microsoft.UI.Xaml.dll
Unhandled exception at 0x5A217FD9 (Microsoft.ui.xaml.dll) in Example.exe: 0xC000027B: An application-internal exception has occurred. (parameters: 0x055D3D88, 0x00000001).

Expected behavior

The app starts normally and navigates to the MainPage.

Screenshots

NuGet package version

1.0.0

Packaging type

Packaged (MSIX)

Windows version

Windows 11 version 21H2 (22000)

IDE

Visual Studio 2022

Additional context

No response

[EP012014]

We need to use a CoreApplication because we're migrating a UWP project to WinUI3, and using the Legacy Desktop model will require a lot of workaround and will impact the UX negatively by the old-fashioned Win32 window and long starting time without Splash screen experience and so on.

[btueffers]

Hi @EP012014, tooling to migrate to desktop, performance improvements, and splash screen support are on our radar. We've captured your feedback and don't currently have any updates to share on those topics. Improving performance is one of our top priorities!

We won't support CoreApplication, but we're working on making migrating easier.

[EP012014]

Hi @EP012014, tooling to migrate to desktop, performance improvements, and splash screen support are on our radar. We've captured your feedback and don't currently have any updates to share on those topics. Improving performance is one of our top priorities!

We won't support CoreApplication, but we're working on making migrating easier.

So why the app crashes while starting and how to fix it? We're using CoreWindow.