Server-Side:

if (!Page.IsPostBack)
            {
                Map1.MapBackground.BackgroundBrush = new GeoSolidBrush(GeoColor.FromHtml("#E5E3DF"));
                Map1.CurrentExtent = new RectangleShape(-180, 90, -180, -90);
                Map1.MapUnit = GeographyUnit.DecimalDegree;

                ContextMenu menuOnEventLayer = new ContextMenu("area", 200);
                ContextMenuItem menu2 = new ContextMenuItem("click me");
                menuOnEventLayer.MenuItems.Add(menu2);
                menu2.OnClientClick = "Test";

                InMemoryFeatureLayer inm1 = new InMemoryFeatureLayer();
                inm1.InternalFeatures.Add(new Feature("LINESTRING(-110.22 40, -80.03 40)"));
                inm1.ZoomLevelSet.ZoomLevel01.DefaultLineStyle = LineStyles.Canal1;
                inm1.ZoomLevelSet.ZoomLevel01.ApplyUntilZoomLevel = ApplyUntilZoomLevel.Level20;


                LayerOverlay ov1 = new LayerOverlay(); ov1.IsBaseOverlay = false;
                ov1.Layers.Add(inm1);

                Map1.CustomOverlays.Add(ov1);

                Feature feature = new Feature(new RectangleShape(-110.22, 50, -80.03, 30));
                Map1.HighlightOverlay.Features.Add("multipolygon", feature);
                Map1.HighlightOverlay.ContextMenu = menuOnEventLayer;
                Map1.HighlightOverlay.Style.FillColor= GeoColor.SimpleColors.Black;
                Map1.HighlightOverlay.HighlightStyle = Map1.HighlightOverlay.Style;
                Map1.HighlightOverlay.Style = new FeatureOverlayStyle(GeoColor.SimpleColors.Black, GeoColor.SimpleColors.Black, 0);
            }

Client-Side:

  <script type="">
         function Test() {
             Map.setLayerIndex(OverlayLayer, 0);
             Map.setLayerIndex(HilightLayer, 100);
             OverlayLayer.redraw(true);
             HilightLayer.redraw(true);
             CurrentContextMenu.display(false);
         }

         var HilightLayer;
         var OverlayLayer;
         var Map;

         function OnMapCreated(map) {
             Map = map;
             OverlayLayer = map.layers[0];
             HilightLayer = map.layers[1];
         }
    </script>