為什么找不到通過綁定程序綁定到附加屬性的Anstor不能工作？

Question

我有一本資源字典，其中包含作為矢量圖形的圖標。 一個附加的屬性允許我定義圖標的顏色。 當我使用圖標作為靜態資源時，從資源字典到附加到圖像的顏色的綁定正在起作用。 但是，當我將綁定與值轉換器一起使用時，顏色綁定不起作用。

有人知道為什么嗎？

這里的用法示例：

<!-- OK, smile is green -->
<Image Source="{StaticResource MaterialMood}" svg:Image.Brush="Green" />

<!-- Not OK, simle is black -->
<Image Source="{Binding Image,Converter={StaticResource GoogleMaterialSource}}" svg:Image.Brush="Green" />

ResourceDictionary.xaml：

<DrawingImage x:Key="MaterialMood" x:Shared="False">
  <DrawingImage.Drawing>
     <DrawingGroup>
        <DrawingGroup>
           <DrawingGroup.ClipGeometry>
              <RectangleGeometry Rect="0,0,24,24" />
           </DrawingGroup.ClipGeometry>
           <GeometryDrawing Brush="{Binding Path=(svg:Image.Brush),RelativeSource={RelativeSource FindAncestor,AncestorType={x:Type Image}},FallbackValue=Black}">
              <GeometryDrawing.Geometry>
                 <PathGeometry FillRule="Nonzero" Figures="M11.99,2C6.47,2 2,6.48 2,12 2,17.52 6.47,22 11.99,22 17.52,22 22,17.52 22,12 22,6.48 17.52,2 11.99,2z M12,20C7.58,20 4,16.42 4,12 4,7.58 7.58,4 12,4 16.42,4 20,7.58 20,12 20,16.42 16.42,20 12,20z M15.5,11C16.33,11 17,10.33 17,9.5 17,8.67 16.33,8 15.5,8 14.67,8 14,8.67 14,9.5 14,10.33 14.67,11 15.5,11z M8.5,11C9.33,11 10,10.33 10,9.5 10,8.67 9.33,8 8.5,8 7.67,8 7,8.67 7,9.5 7,10.33 7.67,11 8.5,11z M12,17.5C14.33,17.5,16.31,16.04,17.11,14L6.89,14C7.69,16.04,9.67,17.5,12,17.5z" />
              </GeometryDrawing.Geometry>
           </GeometryDrawing>
        </DrawingGroup>
     </DrawingGroup>
  </DrawingImage.Drawing>
</DrawingImage>

C＃：

public enum MaterialImage
{
  Mood
}

public class GoogleMaterialSourceConverter : IValueConverter
{
  public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
  {
     if (value == null) return null;

     var imageName = string.Format("Material{0}", value);
     if (!Application.Current.Resources.Contains(imageName)) return null;

     var image = Application.Current.Resources[imageName] as DrawingImage;
     return image == null ? null : image.Clone(); // `x:Shared = false;` ???
  }

  public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
  {
     throw new NotImplementedException();
  }
}

public static class Image
{
  public static readonly DependencyProperty BrushProperty = DependencyProperty.RegisterAttached(
     "Brush",
     typeof(Brush),
     typeof(Image),
     new FrameworkPropertyMetadata(Brushes.Black, FrameworkPropertyMetadataOptions.Inherits));

  [TypeConverter(typeof(BrushConverter))]
  public static Brush GetBrush(DependencyObject element)
  {
     return (Brush)element.GetValue(Image.BrushProperty);
  }

  [TypeConverter(typeof(BrushConverter))]
  public static void SetBrush(DependencyObject element, Brush value)
  {
     element.SetValue(Image.BrushProperty, value);
  }
}

public partial class MainWindow : Window
{
  public static readonly DependencyProperty ImageProperty = DependencyProperty.Register("Image",
     typeof (MaterialImage), typeof (MainWindow), new PropertyMetadata(MaterialImage.Mood));

  public MaterialImage Image
  {
     get { return (MaterialImage)this.GetValue(MainWindow.ImageProperty); }
     set { this.SetValue(MainWindow.ImageProperty, value); }
  }

  public MainWindow()
  {
     this.DataContext = this;
     this.InitializeComponent();
  }
}

Answer 1

感謝King King的評論，我能夠更改代碼，因此現在可以使用了。 現在不再使用IValueConverter綁定到枚舉值，而是使用另一個附加屬性來設置圖像源：

XAML：

<Image svg:Image.Brush="Green" svg:Image.Source="{Binding Image}" />

CS：

public static class Image
{
  // color stuff goes here
  ... 

  public static readonly DependencyProperty SourceProperty = DependencyProperty.RegisterAttached("Source", typeof(MaterialImage), typeof(Image), new FrameworkPropertyMetadata(MaterialImage.Mood, OnSourceChangedCallback));

  public static MaterialImage GetSource(DependencyObject element) { return (MaterialImage)element.GetValue(Image.SourceProperty); }
  public static void SetSource(DependencyObject element, MaterialImage value) { element.SetValue(Image.SourceProperty, value); }

  private static void OnSourceChangedCallback(DependencyObject source, DependencyPropertyChangedEventArgs args)
  {
     var image = (System.Windows.Controls.Image)source;
     if (args.NewValue == null)
     {
        image.Source = null;
        return;
     }

     var resourceName = string.Format("Material{0}", args.NewValue);
     if (!Application.Current.Resources.Contains(resourceName))
     {
        image.Source = null;
        return;
     }

     image.Source = Application.Current.Resources[resourceName] as DrawingImage;
  }
}