var gg = new CLLocationCoordinate2D(37.8197, -122.4786);
var sfo = new CLLocationCoordinate2D(37.6189, -122.3750);
var ggAnnotation = new MKPointAnnotation() { Title = "Golden Gate Bridge", Coordinate = gg };
var sfoAnnotation = new MKPointAnnotation() { Title = "SFO", Coordinate = sfo };

mapView.ShowAnnotations(new MKPointAnnotation[] { ggAnnotation, sfoAnnotation }, false);

var emptyDict = new NSDictionary();
var req = new MKDirectionsRequest() {
	Source = new MKMapItem(new MKPlacemark(gg, emptyDict)),
	Destination = new MKMapItem(new MKPlacemark(sfo, emptyDict)),
	TransportType = MKDirectionsTransportType.Automobile
};

var dir = new MKDirections(req);
dir.CalculateDirections((response, error) => { 
	if(error == null){
		var route = response.Routes[0];
		var rteLine = new MKPolylineRenderer(route.Polyline) {
			LineWidth = 5.0f,
			StrokeColor = UIColor.Purple
		};

		mapView.GetRendererForOverlay = (mv, ol) => rteLine;
		mapView.AddOverlay(route.Polyline, MKOverlayLevel.AboveRoads);
	}else{
		Console.WriteLine(error);
	}
});