public ActionResult AnswerSurvey(int id)
        {
            var selectedSurvey = _context.Surveys.SingleOrDefault(s => s.ID == id);

            var viewModel = new AnswerSurveyFormViewModel()
            {
                Survey = selectedSurvey
            };

            return(View("AnswerSurvey", viewModel));
        }
        public ActionResult Save(SurveyUser surveyUser, int id)
        {
            if (!ModelState.IsValid)
            {
                var viewModel = new AnswerSurveyFormViewModel()
                {
                    SurveyUser = surveyUser,
                };

                return(View("AnswerSurvey", viewModel));
            }

            surveyUser.SurveyID = id;
            _context.SurveyUsers.Add(surveyUser);


            _context.SaveChanges();

            return(RedirectToAction("Index", "SurveyUser"));
        }