Draw on Silverlight Virtual Earth Map Control

There are a couple of different projects where I'd like to enable 'drawing' on a map (including RaceReplay.net) - this is a basic first-cut of drawing within the Microsoft VE Map Control.

Each click on the map will start/continue a line. The MouseLeave event is wired to start a 'new' line. Navigating the map (dragging/double-click zoom) also causes points to be drawn - obviously this needs some work...


The two files required to build it are Page.xaml and Page.xaml.cs, the key pieces of code being

private void VEMap_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    Map m = (Map)sender;
    Location l = m.ViewportPointToLocation(e.GetPosition(m));
    if (polyline == null)
        CreateNewPolyline(l);
    else
        polyline.Locations.Add(l);
}

and

private void CreateNewPolyline(Location startPoint)
{
    polyline = new MapPolyline();
    polyline.Stroke = new SolidColorBrush(Colors.Red);
    polyline.StrokeThickness = 2;
    var lc = new LocationCollection();
    lc.Add(startPoint);
    polyline.Locations = lc;
    VEMap.Children.Add(polyline);
}

Simple, eh?

p.s. these are plain old straight lines - at the 'continent' level you might expect them to curve as though on a great-circle; I'm not too worried about implementing that right now since the target usage of my drawing is at a much "smaller scale"... however Geoquery2008 does draw great circle lines correctly...