Question

In my attempt to create concurrent Socket operations, I’ve created the following code:

ConcurrentQueue<byte[]> messageQueue;
ManualResetEvent resetEvent;
Thread outThread;   // -> new Thread(BeginSending);

public void BeginSending() // invoked by outThread
{
    while (true)
    {
        resetEvent.WaitOne();
        while (messageQueue.Count > 0)
        {
            byte[] msg;
            messageQueue.TryDequeue(out msg);
            // send msg via socket
        }
        resetEvent.Reset();
    }
}

public void QueueMessage(byte[] msg) // invoked by the main thread
{
    messageQueue.Enqueue(msg);
    resetEvent.Set();
}

Is adding items to the ConcurrentQueue while a different thread is iterating/dequeuing it a dangerous thing?

From my understanding many synchronized collections simply have individually synchronized methods, but is the same true for concurrentQueue and similar collections?
(ConcurrentBag, ConcurrentDictionary, ConcurrentStack)

Answer 1

The ConcurrentQueue itself is OK, as long as you are not mutating the arrays stored as its elements.

However, your usage pattern with ManualResetEvent suggests that there is a better solution: if you use BlockingCollection<T>, you would be able to avoid doing manual synchronization.