Amib.Threading.Internal.PriorityQueue.PriorityQueueEnumerator.MoveNext C# (CSharp) Method

            public bool MoveNext()
            {
                if (null == _enumerator)
                {
                    return false;
                }

                if(_version != _priorityQueue._version)
                {
                    throw new InvalidOperationException("The collection has been modified");

                }
                if (!_enumerator.MoveNext())
                {
                    _queueIndex = _priorityQueue.GetNextNonEmptyQueue(_queueIndex);
                    if(-1 == _queueIndex)
                    {
                        return false;
                    }
                    _enumerator = _priorityQueue._queues[_queueIndex].GetEnumerator();
                    _enumerator.MoveNext();
                    return true;
                }
                return true;
            }