silverlight - 如何仅使用 XAML 显示不同的 Enum 图标？

Question

我想根据枚举值显示不同的图标/图像。例如，如果我有以下枚举:

  public enum UploadStatus
  {
      Unknown = 0,
      WaitingToUpload = 10,
      Uploading = 20,
      Uploaded = 30,
      UploadFailed = 40
  }

我想编写如下所示的 XAML:

...

<EnumImage Value="{Binding Path=CurrentStatus}">
  <EnumImageItem Value="Unknown"         Image="/images/unknown.png" />
  <EnumImageItem Value="WaitingToUpload" Image="/images/clock.png" />
  <EnumImageItem Value="Uploading"       Image="/images/upload.png" />
  <EnumImageItem Value="Uploaded"        Image="/images/tick.png" />
  <EnumImageItem Value="UploadFailed"    Image="/images/error.png" />
</EnumImage>

...

我发现许多帖子建议自定义 IValueConverters，但这些解决方案不适合 XAML 范例。

有什么指示或建议吗？

Answer 1

这是一个值转换器，它维护“XAML 范例”，即枚举值和图像之间的关系在 XAML 中维护。

[ContentProperty("Items")]
public class EnumToObjectConverter : IValueConverter
{
    public ResourceDictionary Items { get; set; }

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string key = Enum.GetName(value.GetType(), value);
        return Items[key];
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException("This converter only works for one way binding");
    }
}

请注意，这是非常通用的，它实际上将任何枚举类型的值映射到任何任意对象。这是它在 Xaml 中的用法:-

<Grid.Resources>
  <local:EnumToObjectConverter x:Key="Icons">
    <ResourceDictionary>
 <BitmapImage x:Key="Unknown" UriSource="/images/unknown.png" />
      <BitmapImage x:Key="WaitingToUpload" UriSource="/images/clock.png" />        
      <BitmapImage x:Key="Uploading"       UriSource="/images/upload.png" />        
      <BitmapImage x:Key="Uploaded"        UriSource="/images/tick.png" />        
      <BitmapImage x:Key="UploadFailed"    UriSource="/images/error.png" />        
    </ResourceDictionary>
  </local:EnumToObjectConverter>
</Grid.Resources>

此转换器可以在绑定(bind)枚举类型的属性时使用:-

 <Image Source="{Binding Status, Converter={StaticResource Icons}}" />