public async Task <IActionResult> OnGetAsync(int?pairID) { await CheckRole(_context, _userManager, JoinCode); if (pairID == null) { return(NotFound()); } var id = pairID.GetValueOrDefault(); var pair = await _context.GetPairAsync(id); Courses = pair.Courses; JoinCode = pair.JoinCode; return(Page()); }