public IActionResult DeleteBookFromRepository(string sessionID, int?userID, int?bookID) { if (sessionID == null || userID == null || bookID == null) { return(NullValues()); } var user = VerifyUserSessionID(sessionID, userID); if (user == null) { return(InvalidSessionID()); } var bookToReturn = bookDao.DeleteBookFromDatabase(user, bookID); return(Ok(bookToReturn)); }