TableView.ReloadData equivalent for listView?

I have a listView where the cells have a field that is constantly updated on the backend. I have a timer set up to pull the new data at a set interval, but I don't see anywhere to have the listView refresh itself. For an iOS project I would simply call tableView.ReloadData(). I've tried reassigning the listView.ItemSource property on the main thread, but that didn't work.

I've also tried looking into bindings/observable collections, but those only seem to work for adding/removing items from the list. The number of items in my list aren't going to change, just a property on each item.

Here's a simplified version of the code I'm attempting:

public class Foo {
         List<MyItem> itemList;
         ListView listView;

         public Foo () {
                itemList = new List<MyItem>();

                listView = new ListView();
                listView.ItemTemplate = new DataTemplate (typeof(MyCell));
                listView.ItemsSource = itemList;

                var timer = new Timer (2000);
                timer.Elapsed += OnTimerElapsed;
                timer.Start ();
       }

       public void OnTimerElapsed(object o, ElapsedEventArgs e) {
             Device.BeginInvokeOnMainThread (() => {
                   itemList = beaconLocater.GetAvailableBeacons();
                   listView.ItemsSource = itemList;
              });
        }
}