Database is being used by another process … but what process?

Question

I have written a very small C# program, that uses a very small SQL Server database, purely for some learning & testing purposes. The database is used in this one new pro

Answer 1

IIRC using AttachDbFilename spins up a SqlServr.exe process running under the user account your process is using, separate from the SqlServer instance running as a service (so stopping the MsSqlServer service doesn't stop this issue). In the case of a dirty exit, sometimes this process does not get cleaned up. I suspect that killing this process will free up the db files.