The ActionUpdate event fires when “pending” responses are received during C-Move operations.

The event is therefore triggered by a response on the primary connection indicating how many images:

• Have been sent successfully
• Have Been sent with a warning response
• Have failed
• Are still to be sent

Such pending responses are however optional and the server may choose not to send any.

If this is the case you will find that ActionUpdate does not fire.

DicomObjects based servers send a pending response after every image is sent (or failed).