// GET: AdminPanel
        public async Task <IActionResult> Index(
            int?contestId,
            int?nominationId,
            int page = 1,
            PostsSortState sortOrder = PostsSortState.RatingAsc)
        {
            int pageSize = 10;

            IQueryable <Post> posts = _context.Posts
                                      .Where(x => x.ContestId == contestId)
                                      .Include(x => x.Author)
                                      .Include(x => x.Likes)
                                      .Include(x => x.Nomination);

            //Фильтрация
            if (nominationId != null && nominationId != 0)
            {
                posts = posts.Where(x => x.NominationId == nominationId);
            }

            //Сортировка
            switch (sortOrder)
            {
            case PostsSortState.RatingAsc:
                posts = posts.OrderBy(x => x.Rating);
                break;

            case PostsSortState.RatingDesc:
                posts = posts.OrderByDescending(x => x.Rating);
                break;

            case PostsSortState.NameAsc:
                posts = posts.OrderBy(x => x.Title);
                break;

            case PostsSortState.NameDesc:
                posts = posts.OrderByDescending(x => x.Title);
                break;
            }

            //Пагинация
            var count = await posts.CountAsync();

            var items = await posts.Skip((page - 1) *pageSize).Take(pageSize).ToListAsync();


            PostsIndexViewModel viewModel = new PostsIndexViewModel()
            {
                PageViewModel   = new PostsPageViewModel(count, page, pageSize),
                SortViewModel   = new PostsSortViewModel(sortOrder),
                FilterViewModel = new PostFilterViewModel(_context.Nominations.Where(x => x.ContestId == contestId).ToList(), nominationId),
                Posts           = items,
                HelpNamePost    = new Post()
            };

            ViewBag.ContestId   = contestId;
            ViewBag.ContestName = _context.Contests.FirstOrDefaultAsync(x => x.Id == contestId).Result.Name;

            return(View(viewModel));
        }
        }                                                       // текущее значение сортировки

        public PostsSortViewModel(PostsSortState sortOrder)
        {
            NameSort   = sortOrder == PostsSortState.NameAsc ? PostsSortState.NameDesc : PostsSortState.NameAsc;
            RatingSort = sortOrder == PostsSortState.RatingAsc ? PostsSortState.RatingDesc : PostsSortState.RatingAsc;
            Current    = sortOrder;
        }