Sharepoint 2010 Calendar Event Receiver

I have been tasked with creating a calendar in a root site that get's updated from child site calendar events.

I am able to access the Calendar List from the parent site in the child site's to add an event. However, I'm having trouble finding a way to create a uniqueIdentifier for the event so that when the child calendar's event is updated or deleted, the parent site calendar get's updated as well.

The ListItem ID 开发者_如何学运维field appears to be only unique among the site. I did find a UniqueItemId field, but apparantly it's read-only in the SP LIstitem object.

Can someone please give me some guidance here?

Many thanks!

concatenate the child item's parent web id (Guid) and parent list id (Guid) with the item's id (integer)?

WEBID_LISTID_ITEMID

I discovered you can add a custom field to a list in Sharepoint Designer >> List and Libraries. I then created a Text field to store the Listitem.UniqueID of the child listitem in the parent calendar listitem that I create on the item adding event. Using CAML to search the list in event receiver worked like a charm.