Unable to Change Recurrence Pattern in EWS

Question

I am having a problem that has been reported here and elsewhere before: not being able to change the recurrence pattern on a master via EWS. First, I tried using the old proxy classes against E2010. I have also now tried using the 2.0 Managed API, to no avail. The error FWIW is "Set action is invalid for property". E.g. I want to change the recurrence end date, or the number of recurrences.

In an MSDN post from 2008, Dave Stirling mentions that only the organizer should be able to do this. This is a problem for me because my server application uses a single, full-access id to manage all of the room resource calendars in an enterprise. With this user I can delete appointments on any calendar, regardless of organizer, and I can certainly update a single instance of a recurring series, e.g. changing its start time. I don't understand why manipulating the recurrence pattern would be prohibited because I'm not the organizer while manipulating an instance's spot on the calendar, or deleting the entire series would not be.

I have also tried using impersonation, so that I am (I think) impersonating the Room resource itself, in which case, even though I am not the organizer, I feel I must be the owner of the appointment, and hence entitled to do whatever the heck I want to it. I guess Exchange feels differently. Managed API code below, FWIW.

TIA, Paul

var Svc = new ExchangeService(ExchangeVersion.Exchange2010, TimeZoneInfo.Local);
Svc.CookieContainer = new CookieContainer();
Svc.Credentials = new WebCredentials(m_SvcUser, m_SvcPswd);
Svc.EnableScpLookup = false;
Svc.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, m_RoomMB);
Svc.AutodiscoverUrl(m_RoomMB, RedirectionCallback);
var Master = Appointment.Bind(Svc, new ItemId(args[0]), m_Props);
if (Master.Recurrence.NumberOfOccurrences != null)
    Master.Recurrence.NumberOfOccurrences--;
else
    Master.Recurrence.EndDate = DateTime.Now;
Master.Update(ConflictResolutionMode.AlwaysOverwrite, SendInvitationsOrCancellationsMode.SendToNone);

Answer 1

To close this out, I will report that I opened this question as a support issue after getting no responses here or on MSDN. The net of it is this: Exchange does not permit an attendee (in this case a conference room I am impersonating in EWS) to change the recurrence "blob." This is by design. The only user who can do so is the organizer. I'm not sure this really makes complete sense to me, but I don't have much say in the matter, now do I?