public async Task <IActionResult> OnGet() { if (ClassId == Guid.Empty || SubjectId == Guid.Empty) { TempData["Warning"] = ""; return(RedirectToPage("/Admin/ClassDetails", new { ClassId = ClassId })); } var response = await _data.RemoveSubjectFromClassAsync(ClassId, SubjectId); if (response == null) { TempData["Failed"] = "Operation failed because selected subject does not exist in list"; } else { TempData["Success"] = "Subject successfully remove form list"; } return(RedirectToPage("/Admin/ClassDetails", new { ClassId = ClassId })); }