public virtual async Task <ActionResult> Edit(EditGroupCourseViewModel viewModel)
        {
            var obj = new EditGroupCourseViewModel
            {
                Id     = viewModel.Id,
                Course = _CourseService.GetById(viewModel.Course_Id.Value)
            };

            _GroupCourseService.Update(obj);
            await _unitOfWork.SaveChangesAsync();

            CacheManager.InvalidateChildActionsCache();
            return(RedirectToAction("Index", "GroupCourse"));


            if (viewModel.Course_Id.HasValue)
            {
                PopulateCourcesDropDownList(viewModel.Course_Id.Value);
            }
            else
            {
                PopulateCourcesDropDownList(null);
            }

            return(View(viewModel));
        }
        public void Update(EditGroupCourseViewModel viewModel)
        {
            var obj = GetById(viewModel.Id);

            obj.Course = viewModel.Course;
        }