RoundTripCheckBoxSelector functions very much like CheckBoxSelector. Unlike CheckBoxSelector, it makes a round trip back to the server to update its "checked" status. It will fill the CheckGroup instance with "visible and checked" Check instances when it is clicked.
So, for example, within Link.onClick() method, you will be able to get all the selected rows from CheckGroup instance instead of an empty set. If you use PageableListView component, the CheckGroup will only contains objects in the visible page.