Queue<T>.Dequeue returns null

Question

I have a scenario where

• multiple threads are pushing data on a Queue

• only ONE thread is processing data using code below

code -

  while ( Continue )
  {
        while ( queue.Count > 0 )
        {
             MyObj o = queue.Dequeue();
             someProcess(o);
        }
        myAutoResetEvent.WaitOne();
  }

But sometimes, queue.Dequeue() returns null in the scenario above What gives ?

Answer 1

You need to synchronise the access to the queue. Put lock statements around all code sections that access the queue (both reading and writing). If you access the queue simultaneously from multiple threads the internal structures may be corrupted and just about anything can happen.