✅ IEnum and IQueryable usage.

[AllowAnonymous]
        public async Task<IActionResult> Index(IndexViewModel model, string? filter, SortOption? sort, int? pageIndex)
        {
            var decks = _mtgDbContext.Decks.AsEnumerable();
            var decksIQ = _mtgDbContext.Decks.AsQueryable();


            if (!string.IsNullOrEmpty(filter))
            {
                decks = decks.Where(t => t.Name.Contains(filter, StringComparison.OrdinalIgnoreCase));
            }
            
            if (sort is { } s)
            {
                decks = s switch
                {
                    SortOption.NameDesc => decks.OrderByDescending(t => t.Name),
                    SortOption.NameAsc => decks.OrderBy(t => t.Name),
                    _ => decks.OrderBy(t => t.Name)
                };
            }

            var deckIQ = decks.AsQueryable();
            var pageSize = _configuration.GetValue("PageSize", 3);
            var paginatedList = await PaginatedList<Deck>.CreateAsync(decksIQ, pageIndex ?? 1, pageSize);

            model.Decks = paginatedList;
            model.Filter = filter;
            model.Sort = sort;
            return View(model);
        }

            var deckIQ = decks.AsQueryable();
            var pageSize = _configuration.GetValue("PageSize", 3);
            var paginatedList = await PaginatedList<Deck>.CreateAsync(decksIQ, pageIndex ?? 1, pageSize);