Unique id on AppointmentItem, EWS Managed API 2.0

Hi,

We have previously used the EntryId on an AppointmentItem as a unique id when using the EWS service. However in the latest release of the managed API (2.0) this porperty do not exist.

We are now trying to use the property Item.Id but this id do not seem to be unique.

What I would like to know is; which Item property can be used as a unique identifier? Preferably globally because we are using servers on many different domains.

Thanks,

Nicklas