This repo provides a simple way to detect if a ListView or a GridView is scrolling to the top, or the bottom. You just need to register to the ScrollDetected event and look at the ScrollDirection property included in the ScrollingEventArgs argument.
There's a blogpost explaining what it does (in French) : http://blog.thomasnigro.fr/2014/10/30/listview-et-gridview-detecter-un-scroll-vers-le-haut-ou-vers-le-bas/ However it should be pretty straightforward.
BTW, any improvement is welcomed. Thomas Nigro