public IActionResult Detail(int id)
        {
            DiscountDetailVM vm = new DiscountDetailVM();
            var lstParent       = _courseCategoryService.GetParentCategory();

            vm.lstCategories      = new SelectList(lstParent, "Id", "Name");
            vm.lstChildCategories = null;
            vm.ID = id;
            return(View("Detail", vm));
        }
        public async Task <IActionResult> LoadDiscountHasCourse(int id)
        {
            var _context          = _discountService.GetContext();
            DiscountDetailVM vm   = new DiscountDetailVM();
            var discountHasCourse = await(from d in _context.Discount
                                          join dc in _context.DiscountCourse
                                          on d.Id equals dc.Iddiscount
                                          join c in _context.Courses
                                          on dc.Idcourse equals c.Id
                                          where d.Id == id
                                          select new DiscountDetailVM
            {
                CodeDiscount = d.CodeDiscount,
                NameCourse   = c.Name,
                IdDiscount   = d.Id,
                IdCourse     = c.Id,
                Image        = c.Image
            }).ToListAsync();
            var discountHasNotCourse = await _context.Courses.Where(x => !discountHasCourse.Select(m => m.IdCourse).Any(m => x.Id.Equals(m))).ToListAsync();

            vm.lstDiscountCourse = discountHasCourse;
            vm.lstCourse         = discountHasNotCourse;
            return(Json(new { data = vm, status = vm.lstDiscountCourse.Count > 0 ? true : false }));
        }