Cannot store and retrieve custom ItemProperties from AppointmentItem in case it is a recurring AppointmentItem

问题

I want to add some custom properties on an AppointmentItem. This works perfectly for "normal" AppointmentItems.

Example:

myAppointment.ItemProperties.Add("MyId", Outlook.OlUserPropertyType.olText, false, 1);
MyId = (Outlook.UserProperty)myAppointment.ItemProperties["MyId"];
MyId.Value = myMeeting.id;
meetingId = myMeeting.id;
myAppointment.Save();

Even when I restart Outlook I can fetch those properties from the AppointmentItem like that:

MyId = (Outlook.UserProperty)theCurrentAppointment.ItemProperties["MyId"];                  

No problems so far.

Now when I use the same method in AppointmentItems which represent ONE AppointmentItem within a recurrent appointment series it either does not store or cannot retrieve the MyItem property.

Anyone any idea why it behaves differently when it is a recurring AppointmentItem?

来源：https://stackoverflow.com/questions/55532225/cannot-store-and-retrieve-custom-itemproperties-from-appointmentitem-in-case-it