HashSet<string> x = new HashSet<string>();
List<Task> bagConsumeTasks = new List<Task>();
int itemsInBag = 0;
while (!result.IsEmpty)
{
    bagConsumeTasks.Add(Task.Run(() =>
    {
        string item;
        if (result.TryTake(out item))
        {
            x.Add(item);
            itemsInBag++;
        }
    }));
}
Task.WaitAll(bagConsumeTasks.ToArray());