来自web的WPF图像替代源

我将图像存储到websevers中。如果第一台服务器不可用，我希望有另一个加载图像的路径

比如：

   <Image Source="http://server1/images/image1" 
          AlternativeSource="http://server2/images/image1"/>

---

如何操作？

Lucky for us Image control在加载图像失败时会引发一个事件，因此很容易检查图像加载是否失败

可以采取的一种方法是扩展图像控件

public class AlternativeImage : Image
{

    private bool _tryAlternativeSource ;

    public string AlternativeSource
    {
        get { return (string)GetValue(AlternativeSourceProperty); }
        set { SetValue(AlternativeSourceProperty, value); }
    }

    // Using a DependencyProperty as the backing store for ItemTemplate.  This enables animation, styling, binding, etc...
    public static readonly DependencyProperty AlternativeSourceProperty =
        DependencyProperty.Register("AlternativeSource", typeof(string), typeof(AlternativeImage), new PropertyMetadata(null));

    public AlternativeImage()
    {
        Initialized += OnInitialized;
    }

    private void OnInitialized(object sender, EventArgs eventArgs)
    {
        _tryAlternativeSource = !string.IsNullOrEmpty(AlternativeSource);

        //Note , ths need to be unregistered 
        ImageFailed += OnImageFailed;
    }

    private void OnImageFailed(object sender, ExceptionRoutedEventArgs exceptionRoutedEventArgs)
    {
        if (!_tryAlternativeSource)
            return;

        _tryAlternativeSource = false;

        Source = new ImageSourceConverter().ConvertFromString(AlternativeSource) as ImageSource;
    }
}

然后像这样使用它

<controls:AlternativeImage Source="http://server1/images/image1" 
      AlternativeSource="https://media.licdn.com/mpr/mpr/p/1/005/07f/0e1/07ab226.jpg"/>

上传了完整的代码