We are using MVVM, a DataSource, and a Template to display a list of objects. We have a div rigged up with "source: vehicles", and the "vehicles" variable is a DataSource. We also rig up the DataSource with a Pager, so it doesn't display all vehicles at once. We default the DataSource to a PageSize of 20, then when a user reaches the bottom of the list, it automatically extends the PageSize by 10 (endless scrolling).

The problem with this is that every time the PageSize changes, it redraws every single item that is displayed. So when the PageSize reaches 100-ish and beyond, the browser begins to lag on every PageSize change, since it is redrawing every item every time.

We need an option for the PageSize change to recognize which items are already drawn and only add to the list the new items that need shown.