public IActionResult SelectByCategory()
        {
            var model = new AdvertisementsCategoryFormModel
            {
                Categories = this.category
                             .All()
                             .Select(c => new SelectListItem
                {
                    Text  = c.Name,
                    Value = c.Id.ToString()
                })
            };

            return(View(model));
        }
        public IActionResult SelectByCategory(AdvertisementsCategoryFormModel model)
        {
            if (!ModelState.IsValid)
            {
                model.Categories = this.category
                                   .All()
                                   .Select(c => new SelectListItem
                {
                    Text  = c.Name,
                    Value = c.Id.ToString()
                });
                return(View(model));
            }

            return(RedirectToAction(nameof(AllByCategory), new { categoryId = model.CategoryId }));
        }