public ActionResult Edit(EditViewModel editViewModel)
        {
            if (editViewModel == null)
            {
                throw new HttpException(400, "Bad Request");
            }

            var answer = AnswerService.FindById(editViewModel.AnswerId);
            if (answer == null)
            {
                throw new HttpException(404, "Not Found");
            }

            answer.Content = editViewModel.Content;
            answer.QuestionGroup = QuestionGroupService.FindById(editViewModel.DropDownList_QuestionGroup_Property.SelectedQuestionGroup);
            answer.QuestionGroupId = editViewModel.DropDownList_QuestionGroup_Property.SelectedQuestionGroup != -1 ? (int?)editViewModel.DropDownList_QuestionGroup_Property.SelectedQuestionGroup : null;
            AnswerService.UpdateAnswer(answer);
            TempData["AnswerId"] = answer.AnswerId;
            TempData["AnswerName"] = answer.Content;
            TempData["Message"] = AnswersMessage.EditSuccess;
            return Redirect(Url.Content("~/feedback/answers/index"));
        }
        public ActionResult Edit(int? id)
        {
            if (id == null)
            {
                throw new HttpException(400, "Bad Request");
            }

            var answer = AnswerService.FindById(id.Value);
            if (answer == null)
            {
                throw new HttpException(404, "Not Found");
            }

            var dropdownlist_QuestionGroup_Property = new EditViewModel.DropDownList_QuestionGroup()
            {
                QuestionGroups = QuestionGroupService.GetQuestionGroups().ToList(),
                SelectedQuestionGroup = answer.QuestionGroup != null ? answer.QuestionGroup.QuestionGroupId : -1
            };

            var editViewModel = new EditViewModel()
            {
                AnswerId = answer.AnswerId,
                Content = answer.Content,
                DropDownList_QuestionGroup_Property = dropdownlist_QuestionGroup_Property,
            };
            return View("~/views/feedback/answers/edit.cshtml", editViewModel);
        }