StaticResource标记扩展与System.Windows.Application.FindResource

我在ResourceDictionary中定义了一个位图图像,如下所示:

<BitmapImage x:Key="Skin_Image_Back" UriSource="./images/back.png" />

像那样加载资源字典

var dict = Application.LoadComponent(
   new Uri("TestProject.DefaultStyle;component/Style.xaml",
   UriKind.Relative)) as ResourceDictionary;
Application.Current.Resources.MergedDictionaries.Add(dict);

当我通过XAML和StaticResource标记扩展(如

<Image Source="{StaticResource Skin_Image_Back}" />

一切正常。

但当我想通过以下方式设置源图像时:

MyObject.ImageUrl = FindResource("Skin_Image_Back").ToString();

findresource返回一个uri,它将导致

"pack://application:,,,/TestProject.DefaultStyle;component/images/back.png"

通过一个转换器

<Image Source="{Binding ImageURL, Converter={StaticResource StringToImageThumbSourceConverter}}" />

执行为

<Converter:StringToImageThumbSource x:Key="StringToImageThumbSourceConverter" />

和

  public class StringToImageThumbSource : IValueConverter {
     public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
        try {
           if(value != null) {
              string s = value.ToString();
              if(!string.IsNullOrEmpty(s) && File.Exists(s)) {
                 BitmapImage bi = new BitmapImage();

                 bi.CreateOptions = BitmapCreateOptions.DelayCreation;
                 bi.BeginInit();
                 if(parameter is int) {
                    bi.DecodePixelWidth = (int)parameter;
                    bi.DecodePixelHeight = (int)parameter;
                 }
                 bi.UriSource = new Uri(value.ToString());
                 bi.EndInit();
                 return bi;
              }
           }
        } catch {
        }
        return null;
     }

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

那它就不起作用了…但是为什么呢?