NMS gotcha

I use NMS C# client to get messages from ActiveMQ and I faced a problem: despite there were messages in the queue my "consumer.ReceiveNoWait()" returned nothing.

After some code reading I realized the reason. My code looked like

using (IMessageConsumer consumer = session.CreateConsumer(queue, filter))
IMessage oldMessage;
while ((oldMessage = consumer.ReceiveNoWait() != null)
...

Apparently ReceiveNoWait does not send any request to the queue server. What it does is checking its own buffer of received messages.
When you create a Message Consumer then you notify the queue server that you want to receive messages from certain Target (Queue). But messages are not sent as registration response. So you have consumer registered but no messages yet.
Now, if you try to call consumer.ReceiveNoWait() right after registration you will get null. You need to wait a little bit before queue will send messages to the consumer.

/
Adding 100ms wait helps to address this problem:

using (IMessageConsumer consumer = session.CreateConsumer(queue, filter))
IMessage oldMessage;
while ((oldMessage = consumer.Receive(TimeSpan.FromMilliseconds(100))) != null)
...