Describe the bug

Single-project MSIX throws Markup.XamlParseException: 'XAML parsing failed.' when using templated control from ClassLibrary referenced by dll.

Steps to reproduce the bug

Steps to reproduce:

1. Create WinUI class library
2. Add empty custom control to the project
3. Create a new Single-project MSIX project
4. Add a new reference to dll of the class library
5. Add custom control from class library to MainWindow.xaml
6. Run project

WinUIRes.zip

Expected behavior

You can also create a new solution with a separate packaging project and repeat step 3,4,5,6 - it works fine

Screenshots

No response

NuGet package version

No response

Windows app type

• UWP
• Win32

Device form factor

Desktop

Windows version

May 2021 Update (19043)

Additional context

No response