XAML-Map-Control/MapUiTools/Shared/MapLayerMenuItem.cs

using System;
using System.Linq;
using System.Threading.Tasks;
#if WPF
using System.Windows;
using System.Windows.Markup;
#elif UWP
using Windows.UI.Xaml;
using Windows.UI.Xaml.Markup;
#elif WINUI
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Markup;
#else
using Avalonia.Metadata;
using FrameworkElement = Avalonia.Controls.Control;
#endif

namespace MapControl.UiTools
{
#if WPF
    [ContentProperty(nameof(MapLayer))]
#elif UWP || WINUI
    [ContentProperty(Name = nameof(MapLayer))]
#endif
    public class MapLayerMenuItem : MapMenuItem
    {
#if AVALONIA
        [Content]
#endif
        public FrameworkElement MapLayer { get; set; }

        public Func<Task<FrameworkElement>> MapLayerFactory { get; set; }

        public MapLayerMenuItem()
        {
            Click += async (s, e) =>
            {
                if (DataContext is MapBase map)
                {
                    await Execute(map);

                    foreach (var item in ParentMenuItems.OfType<MapLayerMenuItem>())
                    {
                        item.IsChecked = map.Children.Contains(item.MapLayer);
                    }
                }
            };
        }

        public virtual async Task Execute(MapBase map)
        {
            map.MapLayer = MapLayer ?? (MapLayer = await MapLayerFactory.Invoke());
            IsChecked = true;
        }
    }

    public class MapOverlayMenuItem : MapLayerMenuItem
    {
        public override async Task Execute(MapBase map)
        {
            var layer = MapLayer ?? (MapLayer = await MapLayerFactory.Invoke());

            if (map.Children.Contains(layer))
            {
                map.Children.Remove(layer);
            }
            else
            {
                var index = 1;

                foreach (var itemLayer in ParentMenuItems?
                    .OfType<MapOverlayMenuItem>()
                    .Select(item => item.MapLayer)
                    .Where(itemLayer => itemLayer != null))
                {
                    if (itemLayer == layer)
                    {
                        map.Children.Insert(index, itemLayer);
                        break;
                    }

                    if (map.Children.Contains(itemLayer))
                    {
                        index++;
                    }
                }
            }
        }
    }
}