public async Task <IActionResult> GradeStudent(int id, string studentId, Grade grade) { if (string.IsNullOrEmpty(studentId)) { return(BadRequest()); } var userId = _userManager.GetUserId(this.User); if (!await _trainerService.IsTrainer(id, userId)) { return(BadRequest()); } var success = await _trainerService.AddGradeAsync(id, studentId, grade); if (!success) { return(BadRequest()); } return(this.RedirectToAction(nameof(Students), new { id })); }