Delayed Acknowledgements when synchronously sending messages to Solace broker

When synchronously sending messages to solace in a loop, I only get one callback per second. However, the strange thing is, if I first send a message with the callback set to null, I get the callbacks back-to-back without any delay.

for (int i = 0; i < 10; i++)
{    
	sender.Send(message,
	  (ILink l, Message m, Outcome o, object s) =>
	  {
		Console.WriteLine(DateTime.Now.ToString("o") + ": " + o);
	  },
	  null);
}

  
// When first sending one message with callback set to null, we get the callbacks without delay
 sender.Send(message, null, null);

for (int i = 0; i < 10; i++)
{    
	sender.Send(message,
	  (ILink l, Message m, Outcome o, object s) =>
	  {
		Console.WriteLine(DateTime.Now.ToString("o") + ": " + o);
	  },
	  null);
}

I know that solace takes into account the batchable flag which is described in the AMQP spec (see: http://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-transport-v1.0-os.html)

This probably leads to the delayed acks. But why does sending an unacked message first have influence on the behaviour? Does this lead to batching messages in amqpnetlite? Is this the correct behaviour?

[xinchen10]

Both suggestions make sense. I am looking at ways to give user more control on the protocol performatives.

[joerg-fischer]

In the meantime, I made a modification to the WriteDelivery method in the session class to set batchable to false. I can confirm that now everything works as expected and the receiver does no longer wait for more messages to arrive before sending a disposition frame.