You seem to be looking at this problem from the wrong direction... in MVVM, you can pretty much forget about the UI for the most part. So, instead of thinking how to get hold of the item that the user added into the collection control in the UI, think about accessing the data object that you added to the data collection in the view model that is data bound to the UI collection control in response to an ICommand
that was initiated by the user.
So to me, it sounds like you need to implement an ICommand
that is connected to a Button
in the UI, where you add the new item into the data bound collection rather than any event. In this way, you'll always know the state of all of your data items.