protected override void HighlightRoutes()
            {
                var btnLt = _outer.FindViewById <Button> (Resource.Id.buttonLt);
                var btnRt = _outer.FindViewById <Button> (Resource.Id.buttonRt);

                btnRt.Enabled = _highlighedIndex != (_pointDrawingInfos.Count - 1);
                btnLt.Enabled = _highlighedIndex != 0;

                _routeLines.ForEach(x => x.Remove());
                _routeLines.Clear();

                _markers.ForEach(x => x.Remove());
                _markers.Clear();

                var mapPointText = _outer.FindViewById <Button> (MapPointTextId);

                mapPointText.Text = _pointDrawingInfos [_highlighedIndex].Point.Name;

                var map = _mapFragment.Map;

                foreach (var pdi in _pointDrawingInfos)
                {
                    // draw markers
                    MapPoint mPlace = pdi.Point;
                    var      marker = new MarkerOptions();
                    if (pdi != _highlighedPoint)
                    {
                        marker.InvokeAlpha(0.5f);
                    }
                    marker.SetPosition(new LatLng(mPlace.Loc.Lat, mPlace.Loc.Lng));
                    marker.SetTitle(mPlace.Name);
                    _markers.Add(map.AddMarker(marker));

                    DrawPolyline(pdi.Polyline);
                }
            }