XAML-Map-Control/MapControl/WPF/DrawingTile.WPF.cs

using System;
using System.Threading.Tasks;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Media.Imaging;

namespace MapControl;

public class DrawingTile : Tile
{
    public DrawingTile(int zoomLevel, int x, int y, int columnCount)
        : base(zoomLevel, x, y, columnCount)
    {
        Drawing.Children.Add(ImageDrawing);
    }

    public DrawingGroup Drawing { get; } = new DrawingGroup();

    public ImageDrawing ImageDrawing { get; } = new ImageDrawing();

    public override async Task LoadImageAsync(Func<Task<ImageSource>> loadImageFunc)
    {
        var image = await loadImageFunc().ConfigureAwait(false);

        void SetImageSource()
        {
            ImageDrawing.ImageSource = image;

            if (image != null && MapBase.ImageFadeDuration > TimeSpan.Zero)
            {
                if (image is BitmapSource bitmap && !bitmap.IsFrozen && bitmap.IsDownloading)
                {
                    bitmap.DownloadCompleted += BitmapDownloadCompleted;
                    bitmap.DownloadFailed += BitmapDownloadFailed;
                }
                else
                {
                    BeginFadeInAnimation();
                }
            }
        }

        await Drawing.Dispatcher.InvokeAsync(SetImageSource);
    }

    private void BeginFadeInAnimation()
    {
        var fadeInAnimation = new DoubleAnimation
        {
            From = 0d,
            Duration = MapBase.ImageFadeDuration,
            FillBehavior = FillBehavior.Stop
        };

        Drawing.BeginAnimation(DrawingGroup.OpacityProperty, fadeInAnimation);
    }

    private void BitmapDownloadCompleted(object sender, EventArgs e)
    {
        var bitmap = (BitmapSource)sender;

        bitmap.DownloadCompleted -= BitmapDownloadCompleted;
        bitmap.DownloadFailed -= BitmapDownloadFailed;

        BeginFadeInAnimation();
    }

    private void BitmapDownloadFailed(object sender, ExceptionEventArgs e)
    {
        var bitmap = (BitmapSource)sender;

        bitmap.DownloadCompleted -= BitmapDownloadCompleted;
        bitmap.DownloadFailed -= BitmapDownloadFailed;

        ImageDrawing.ImageSource = null;
    }
}