protected Message PeekWithoutTimeout(MessageQueue q, Cursor cursor, PeekAction action)
{
	Message ret = null;
	try
	{
		ret = q.Peek(new TimeSpan(1), cursor, action);
	}
	catch (MessageQueueException mqe)
	{
		if (!mqe.Message.ToLower().Contains("timeout"))
		{
			throw;
		}
	}
	return ret;
}

protected int GetMessageCount(MessageQueue q)
{
	int count = 0;
	Cursor cursor = q.CreateCursor();

	Message m = PeekWithoutTimeout(q, cursor, PeekAction.Current);
	if (m != null)
	{
		count = 1;
		while ((m = PeekWithoutTimeout(q, cursor, PeekAction.Next)) != null)
		{
			count++;
		}
	}
	return count;			
}

Counting Messages in an MSMQ MessageQueue from C#

Counting Messages in an MSMQ MessageQueue

C#