I have a app which takes all the contacts from phone book and check them in my server to check if they are present or not. For which I normally take all the phone numbers each time and check for the sync.
What I want to know if there is any key which is attached to a contact item and we can change with our value so we dont have to send all numbers to server each time, we will just send those numbers which do not have value set by us. In this way we can differentiate the synced and unsynced numbers?