public object Dequeue()
{
object item = _queue.DequeueBlocking();
int count = Interlocked.Decrement(ref _itemCount);
if ( _underThreshold != null )
{
if ( count == _lowerBound )
{
_underThreshold.BeginInvoke(
count, new AsyncCallback(OnAsyncCallEnd),
_underThreshold
);
}
}
return item;
}