XAML-Map-Control/MapControl/Tile.cs

// WPF MapControl - http://wpfmapcontrol.codeplex.com/
// Copyright © 2012 Clemens Fischer
// Licensed under the Microsoft Public License (Ms-PL)

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

namespace MapControl
{
    internal class Tile
    {
        private static readonly DoubleAnimation opacityAnimation = new DoubleAnimation(0d, 1d, TimeSpan.FromSeconds(0.5), FillBehavior.Stop);

        public readonly int ZoomLevel;
        public readonly int X;
        public readonly int Y;
        public readonly ImageBrush Brush = new ImageBrush();

        public Tile(int zoomLevel, int x, int y)
        {
            ZoomLevel = zoomLevel;
            X = x;
            Y = y;
        }

        public Uri Uri { get; set; }

        public int XIndex
        {
            get
            {
                int numTiles = 1 << ZoomLevel;
                return ((X % numTiles) + numTiles) % numTiles;
            }
        }

        public ImageSource Image
        {
            get { return Brush.ImageSource; }
            set
            {
                if (Brush.ImageSource == null)
                {
                    BitmapImage bitmap = value as BitmapImage;

                    if (bitmap != null && bitmap.IsDownloading)
                    {
                        bitmap.DownloadCompleted += BitmapDownloadCompleted;
                        bitmap.DownloadFailed += BitmapDownloadFailed;
                    }
                    else
                    {
                        Brush.BeginAnimation(ImageBrush.OpacityProperty, opacityAnimation);
                    }
                }

                Brush.ImageSource = value;
            }
        }

        private void BitmapDownloadCompleted(object sender, EventArgs e)
        {
            ((BitmapImage)sender).DownloadCompleted -= BitmapDownloadCompleted;
            ((BitmapImage)sender).DownloadFailed -= BitmapDownloadFailed;
            Brush.BeginAnimation(ImageBrush.OpacityProperty, opacityAnimation);
        }

        private void BitmapDownloadFailed(object sender, ExceptionEventArgs e)
        {
            ((BitmapImage)sender).DownloadCompleted -= BitmapDownloadCompleted;
            ((BitmapImage)sender).DownloadFailed -= BitmapDownloadFailed;
            Brush.ImageSource = null;
        }
    }
}