WPF使用MediaElement显示gif图片

使用MediaElement来显示gif图片，封装控件代码如下：
Xaml：

<UserControl x:Class="giftest01.GifImage"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:local="clr-namespace:giftest01"
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Border BorderBrush="{Binding RelativeSource={RelativeSource TemplatedParent},Path=BorderBrush}" 
            BorderThickness="{Binding RelativeSource={RelativeSource TemplatedParent},Path=BorderThickness}">
        <MediaElement x:Name="gifMedia"  MediaEnded="gifMedia_MediaEnded" UnloadedBehavior="Manual"  LoadedBehavior="Play" />
    Border>
UserControl>

cs：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace giftest01
{
    /// 

    /// GifImage.xaml 的交互逻辑
    /// 
    public partial class GifImage : UserControl
    {
        public GifImage()
        {
            InitializeComponent();
        }



        public Uri Source
        {
            get { return (Uri)GetValue(SourceProperty); }
            set { SetValue(SourceProperty, value); }
        }

        // Using a DependencyProperty as the backing store for MyProperty.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty SourceProperty =
            DependencyProperty.Register("Source", typeof(Uri), typeof(GifImage), new PropertyMetadata(null,(sender,p)=> {
                (sender as GifImage).UpdateSource();
            }));

        private void UpdateSource()
        {
            gifMedia.Source = Source;
            gifMedia.Play();
        }


        private void gifMedia_MediaEnded(object sender, RoutedEventArgs e)
        {
            gifMedia.Position = new TimeSpan(0, 0, 1);
            gifMedia.Play();

        }
    }
}