This question shows up when searching "How to clear Visual Studio cache".
I asked that question referring to "the build cache", i.e. I was seeing Build errors that seemed like wrong/outdated error.
For example, Project A referenced Project B, and Project A used BType defined in Project B. But I got an error, like the enum wasn't defined, even though it was clearly defined in Project B.
Using "Clean Solution" did not work for me, the Build errors persisted.
Instead I modified the references of Project "A", removed the "Project B" reference, and re-added it.
I don't know why that helped, I think I was using a "project" type reference before and after (vs using a "dll" reference)... But the build errors stopped.