Can't tap into Scrolled event in ListView in iOS (haven't tried Android)

I'm trying to register an event handler in a custom ListViewRenderer and it looks like this:

this.Control.Scrolled += (object sender, EventArgs ev) => {
    Console.WriteLine("Scrolled!");
};

..but keep getting this error 'Event registration is overwriting existing delegate. Either just use events or your own delegate:'

Any information I've found on this hasn't led me to the correct way to fix this.. this has surely got to be possible. If not, I guess I could leave Forms and set this up manually but would rather stick with Forms. Anybody have any clues?