private async Task <IEnumerable <Item> > RetrieveArticles(int articleCount, IList <int> itemIds) { var items = new List <Item>(); int i = 0; while (i < articleCount) { var itemId = itemIds[i]; var item = await client.GetCachedAsync <Item>($"https://hacker-news.firebaseio.com/v0/item/{itemId}.json", TimeSpan.FromDays(2)); if (item != null) { items.Add(item); } i++; } return(items); }