private void _Click(object sender, EventArgs e)
        {
            foreach (ToolStripMenuItem menu in DropDownItems)
            {
                menu.Checked = false;
            }
            while (mapbox.Map.BackgroundLayer.Count > 0)
            {
                mapbox.Map.BackgroundLayer.RemoveAt(0);
            }
            MapToolStripMenuItem selectedOption = (MapToolStripMenuItem)sender;

            mapbox.Map.BackgroundLayer.Add(new TileAsyncLayer(mnuOpenStreetMap.TileSource, mnuOpenStreetMap.Name));
            TileAsyncLayer mapLayer = new TileAsyncLayer(selectedOption.TileSource, selectedOption.Name)
            {
                OnlyRedrawWhenComplete = true,
            };

            mapbox.Map.BackgroundLayer.Add(mapLayer);
            selectedOption.Checked = true;
            opacitySlider.Visible  = !selectedOption.Name.Equals(mnuOpenStreetMap.Name);
            UpdateLinkLabel(selectedOption.LinkLabelType);
            Application.UserAppDataRegistry.SetValue("Default Map Background", selectedOption.Name);
            mapbox.Refresh();
        }
        private void SetupDropdown()
        {
            TileSourceFactory factory = new TileSourceFactory();

            mnuOpenStreetMap   = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.OpenStreetMap), LinkLabelType.OSM);
            mnuOpenHistoricMap = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.OpenHistoricMap), LinkLabelType.OSM);
            mnuBingMapAerial   = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.BingAerial), LinkLabelType.BING);
            mnuBingMapRoads    = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.BingRoads), LinkLabelType.BING);
            mnuBingMapHybrid   = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.BingHybrid), LinkLabelType.BING);
            mnuNLS1843_1882    = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.NLS_1843_1882_OS_6in), LinkLabelType.NLS);
            mnuNLS1885_1900    = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.NLS_1885_1900_OS_1in), LinkLabelType.NLS);
            mnuNLS1921_1930    = new MapToolStripMenuItem(factory.CreateTileSource(TileSourceFactory.TileType.NLS_1921_1930_OS_6in), LinkLabelType.NLS);

            mnuOpenStreetMap.SetupMapToolStripMenuItem("mnuOpenStreetMap", "Open Street Map", new EventHandler(_Click));
            mnuOpenHistoricMap.SetupMapToolStripMenuItem("mnuOpenHistoricMap", "Open Historical Map 1920-1940 UK", new EventHandler(_Click));
            mnuBingMapAerial.SetupMapToolStripMenuItem("mnuBingMapAerial", "Aerial Bing Map", new EventHandler(_Click));
            mnuBingMapRoads.SetupMapToolStripMenuItem("mnuBingMapRoads", "Roads Bing Map", new EventHandler(_Click));
            mnuBingMapHybrid.SetupMapToolStripMenuItem("mnuBingMapHybrid", "Hybrid Bing Map", new EventHandler(_Click));
            mnuNLS1843_1882.SetupMapToolStripMenuItem("mnuNLS1843_1882", "NLS 1843-1882 OS 6in UK Map", new EventHandler(_Click));
            mnuNLS1885_1900.SetupMapToolStripMenuItem("mnuNLS1885_1900", "NLS 1885-1900 OS 1in UK Map", new EventHandler(_Click));
            mnuNLS1921_1930.SetupMapToolStripMenuItem("mnuNLS1921_1930", "NLS 1921-1930 OS 6in Scotland Map", new EventHandler(_Click));

            // Setup map selector menu
            DisplayStyle = ToolStripItemDisplayStyle.Text;
            DropDownItems.AddRange(new ToolStripItem[] {
                mnuOpenStreetMap,
                mnuOpenHistoricMap,
                mnuBingMapAerial,
                mnuBingMapRoads,
                mnuBingMapHybrid,
                mnuNLS1843_1882,
                mnuNLS1885_1900,
                mnuNLS1921_1930
            });
            ImageTransparentColor = Color.Magenta;
            Name = "mnuMapStyle";
            Size = new Size(71, 22);
            Text = "Map style";
        }