protected override async Task OnParametersSetAsync() { if (_categories.Count == 0) { return; } if (CategoryId == null) { var defaultCategory = _categories.First(); CategoryId = defaultCategory.Id; var newUrl = $"/books/{CategoryId}/{defaultCategory.CategoryName?.Replace(" ", "-")}"; NavigationManager.NavigateTo(newUrl); } _books = await BookWebService.GetBooksByCategory((int)CategoryId); await base.OnParametersSetAsync(); }