[0.8 Preview] Building class library with XAML controls in Release config fails

[andrewleader]

Describe the bug
This is a known issue that affects the 0.8 Preview. If you have a WinUI 3 class library that defines XAML controls and are using the 0.8 Preview, attempting to build your app in Release config will fail with the error seen below. The stable 0.5 release is not affected by this issue.

Error    MSB3030
Could not copy the file
"C:\Users\aleader\source\repos\App24Experimental\ClassLibrary1\bin\x86\Release\net5.0-windows10.0.19041.0\UserControl1.xbf"
because it was not found.     ClassLibrary1 C:\Users\aleader\.nuget\packages\microsoft.projectreunion.foundation\0.8.0-preview\build\Microsoft.ApplicationModel.Resources.PriGen.targets

Workaround
Add <GenerateLibraryLayout>true</GenerateLibraryLayout> to your class library.

We've fixed this with pull request #917 but there is not yet a new version available with this fix.

Steps to reproduce the bug

1. Create a 0.8 Preview WinUI 3 desktop app
2. Add a 0.8 Preview WinUI 3 class library
3. Add a new UserControl (which uses a XAML page)
4. Reference the class library from the desktop app
5. In your desktop app, use the UserControl you defined
6. Attempt to build the app in Release config

Expected behavior
App should build successfully.

Version Info

NuGet package version:
0.8.0-preview

[andrewleader]

Closing as this has been fixed with pull request #917, but note that no release with the fix is available yet.

[huichen123]

a possible workaround is to add <GenerateLibraryLayout>true</GenerateLibraryLayout> in csproj.