private async Task <Item[]> GetNonStoredItemsAsync(IEnumerable <int> newStories)
{
var itemsToBeRetrieved = new List <Task <Item> >();
foreach (var id in newStories)
{
if (!_items.ContainsKey(id))
{
itemsToBeRetrieved.Add(_hackerNewsService.GetItemAsync(id));
}
}
return(await Task.WhenAll(itemsToBeRetrieved));
}