Sometimes contacts may be modified outside of your app. You can use the
ContactStore change tracking API to retrieve a list of changes that have occurred to contacts since a previous point in time.
To establish the current revision number of the contact store, retrieve the value of the
RevisionNumber property. This is an unsigned
long value that is updated whenever a contact is added or removed from the contact store, or whenever a contact is modified.
ContactStore store = await ContactStore.CreateOrOpenAsync();ulong revisionCode = store.RevisionNumber;
You retrieve the list of changes since the last revision by calling the