This project serves as a reproducible for this VS Developer Community issue.

In VS Community 17.8 Preview 5, Im running into the above issue as well as the RZ10012 in blazor components and I believe the problem has to do with UseArtifactsOutput.

Currently this project is in a functional state, to show the issue please follow the steps below:

1. Change UseArtifactsOutput to true in Directory.Build.props
2. Close visual studio
3. Delete the \bin and \obj folders under the Client project (skipping this step will only partially show the issues)
4. Open the solution

After following the steps above you should see compile errors in Program.cs and RZ10012 errors in any blazor component (Home.razor has an example of both first (PageTitle) and third (MudText) party blazor component usage).