public void Enqueue(object item)
{
_queue.EnqueueBlocking(item);
int count = Interlocked.Increment(ref _itemCount);
if ( _overThreshold != null )
{
if ( count == _upperBound )
{
_overThreshold.BeginInvoke(
count, new AsyncCallback(OnAsyncCallEnd),
_overThreshold
);
}
}
}