AnimatedImage.xaml.cs

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using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Media.Imaging;

namespace PhotoSharingApp.Universal.Controls
{
    /// <summary>
    /// An image control that allows specifying a placeholder image
    /// and that fades in the actual image once it has been loaded.
    /// </summary>
    public sealed partial class AnimatedImage : UserControl
    {
        /// <summary>
        /// The dependency property for the image source.
        /// </summary>
        public static readonly DependencyProperty SourceProperty =
            DependencyProperty.Register("Source", typeof(ImageSource), typeof(AnimatedImage),
                new PropertyMetadata(default(ImageSource), SourcePropertyChanged));

        /// <summary>
        /// The dependency property for the placeholder.
        /// </summary>
        public static readonly DependencyProperty PlaceHolderProperty =
            DependencyProperty.Register("PlaceHolder", typeof(ImageSource), typeof(AnimatedImage),
                new PropertyMetadata(default(ImageSource)));

        private readonly bool areAnimationsEnabled = true;

        /// <summary>
        /// The constructor.
        /// </summary>
        public AnimatedImage()
        {
            InitializeComponent();
        }

        /// <summary>
        /// Gets or sets the place holder image.
        /// </summary>
        /// <remarks>
        /// This image is shown until the desired image has been loaded.
        /// </remarks>
        public ImageSource PlaceHolder
        {
            get { return (ImageSource)GetValue(PlaceHolderProperty); }
            set { SetValue(PlaceHolderProperty, value); }
        }

        /// <summary>
        /// Gets or sets the source image.
        /// </summary>
        public ImageSource Source
        {
            get { return (ImageSource)GetValue(SourceProperty); }
            set { SetValue(SourceProperty, value); }
        }

        private void LoadImage()
        {
            imageFadeInStoryboard.Completed += (s, e) =>
            {
                PlaceHolder = null;
                placeHolderImage.Source = null;
            };

            imageFadeInStoryboard.Begin();
        }

        private void OnSourceChanged()
        {
            if (Source != null)
            {
                placeHolderImage.Source = PlaceHolder;
                var bitmapImage = Source as BitmapImage;

                if (bitmapImage != null)
                {
                    image.Source = bitmapImage;

                    if (areAnimationsEnabled)
                    {
                        bitmapImage.ImageOpened += (sender, args) => LoadImage();
                    }
                    else
                    {
                        image.Opacity = 1.0;
                    }
                }
            }
        }

        private static void SourcePropertyChanged(DependencyObject dependencyObject,
            DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
        {
            var control = dependencyObject as AnimatedImage;

            control?.OnSourceChanged();
        }
    }
}