how to access the underlying default concurrent queue of a blocking collection

Question

I have multiple producers and a single consumer. However if there is something in the queue that is not yet consumed a producer should not queue it again. (unique no duplica

Answer 1

This is an interesting question. This is the first time I have seen someone ask for a blocking queue that ignores duplicates. Oddly enough I could find nothing like what you want that already exists in the BCL. I say this is odd because BlockingCollection can accept a IProducerConsumerCollection as the underlying collection which has the TryAdd method that is advertised as being able to fail when duplicates are detected. The problem is that I see no concrete implementation of IProducerConsumerCollection that prevents duplicates. At least we can write our own.

public class NoDuplicatesConcurrentQueue : IProducerConsumerCollection
{
  // TODO: You will need to fully implement IProducerConsumerCollection.

  private Queue queue = new Queue();

  public bool TryAdd(T item)
  {
    lock (queue)
    {
      if (!queue.Contains(item))
      {
        queue.Enqueue(item);
        return true;
      }
      return false;
    }
  }

  public bool TryTake(out T item)
  {
    lock (queue)
    {
      item = null;
      if (queue.Count > 0)
      {
        item = queue.Dequeue();
      }
      return item != null;
    }
  }
}

Now that we have our IProducerConsumerCollection that does not accept duplicates we can use it like this:

public class Example
{
  private BlockingCollection