How to receive the notification from Exchange when a participant was add or delete in an existing appointment

Question

I use the EWS managed API "SubscribeToPushNotifications" to get the notification from Exchange when an appointment is created or modified. It works successfully that I can receive the notifications from Exchange when an appointment is created or modified.

But when I just add or delete a participant in an existing appointment and save(send) this appointment. I can not receive the nofitication from Exchange.

My Question is how to receive the notification from Exchane when I just add or delete a participant in an existing appointment.

By the way, the paramenter of EWS manage API "SubscribeToPushNotifications" I used

new FolderId(WellKnownFolderName.Calendar, new Mailbox(<meetingroom mail address>))
new EventType[] { EventType.Moved, EventType.Created, EventType.Modified }

Answer 1

Add/removing attendees will modify the appointment so should generate a EventType.Modified event in the Organizers calendar. If your looking at events in Attendees or Meeting Rooms (which from you code you appear to be doing) then these calendars will only update based on the recipient and processing of a Meeting Update. Appointments in Exchange are separate store items so the appointment Item in the Organizers Calendar can be change independently on the attendees. The only time the attendees/resource calendar appointment will update is when an update is specifically sent which only happens under certain circumstances. Eg if you just adding an attendee you don't need to notify other attendees (because you not changing the time etc) so an update may or may not be sent (depends on entirely on the client making the update).