Thanks for this.

I suppose the second paragraph means I shouldn't write to this property?

The first para is a great help though I have clearly misunderstood something
I read (or read some internet garbage), and it sounds like I can just use a
user property. Will try that tomorrow.

Thanks

Alan

"Ken Slovak - [MVP - Outlook]" wrote:

Both UserProperties and MAPI named properties on items should remain on
those items even if they're moved. I also don't see why creating a
UserProperty would one-off an item unless the item is using a custom form.

Once a global ObjectID property is assigned to an item it's supposed to not
change, that's the entire purpose of that property. Since EntryID may change
when an item is moved or deleted, depending on the store provider, that
property was created to allow tracking of changed meetings and appointments
despite EntryID changes.

--
Ken Slovak
[MVP - Outlook]
http://www.slovaktech.com
Author: Professional Programming Outlook 2007.
Reminder Manager, Extended Reminders, Attachment Options.
http://www.slovaktech.com/products.htm


"AlanGlover" wrote in message
...
I'm writing an Outlook Add-in to link calendar appointments with room
bookings in our room and resources booking application. I need to store a
room booking reference with the calendar appointment so that if they move
or
delete the appointment I can move or delete the room booking.

I don't want to use the outlook item user properties as this makes the
appointment a "one-off" non-standard item.

I tried using the globalObjId MAPI property (because I noticed this is
where
Outlook stores the UID when an iCal or vCal is received). But Outlook (or
something) changes this property from time to time and I lose my
reference.

I tried creating a named property and this is OK unless the user deletes
an
appointment using the right mouse button menu. In this case I catch the
Item_Add event in the Deleted Items folder but when I look in the
MAPIObject
my named property has dissappeared.

Do named properties get lost when items are moved from folder to folder?
Is
there any safe place I can store my booking reference?