Question

在我的Windows应用商店应用中，我有一个CueAnswerButton用户控件。它包含一个Image控件，它绑定到视图模型中的{Binding NormalImage}。但是我在CueAnswerButton中有其他控件和属性，只要绑定属性发生变化就需要更新（我想在CueAnswerButton中更改时执行代码）。

我该怎么办？

我发现other articles解释了类似的东西，但并不完全。也许我不知道用于找到答案的正确术语。

感谢您的帮助。

// View data model for a cue answer button.

public class CueAnswerViewData : DependencyObject
{
  public CueAnswerViewData()
  {
  }

  public const string NormalImagePropertyTag = "NormalImageProperty";
  public static readonly DependencyProperty NormalImageProperty =
     DependencyProperty.Register(
         NormalImagePropertyTag,
         typeof(ImageSource),
         typeof(CueAnswerViewData),
         new PropertyMetadata(null));
  public ImageSource NormalImage
  {
    get
    {
      return (ImageSource)GetValue(
        NormalImageProperty);
    }
    set
    {
      SetValue(NormalImageProperty, value);
    }
  }

和CueAnswerButton.xaml：

  <Grid>
    <Button x:Name="m_button" 
            HorizontalAlignment="Stretch" 
            VerticalAlignment="Stretch" 
            BorderThickness="0"
            />

    <Image x:Name="m_image" 
           HorizontalAlignment="Stretch" 
           VerticalAlignment="Stretch" 
           Stretch="Fill"
           Source="{Binding NormalImage}" 
           />

    ...

基本上我想在ViewData的NormalImage属性发生变化时调用CueAnswerButton.updateSkinnableProperties（）。是的，这是一个wp7应用程序的端口:)，它仍在进行中。

private void updateSkinnableProperties()
{
  bool skinned = isSkinned();

  m_image.IsHitTestVisible = skinned;
  m_button.IsHitTestVisible = !skinned;

  Background = m_correctHint ? m_correctAnswerGreenBrush : null;
  m_textbox.Background = m_correctHint ? m_correctAnswerGreenBrush : null;
  m_button.Background = m_correctHint ? m_correctAnswerGreenBrush : 
    m_phoneBackgroundBrush;

  m_button.BorderThickness = (skinned || m_correctHint) ?
    m_zeroThickness : m_phoneBorderThickness;

  m_textbox.Foreground = (skinned || m_correctHint) ?
    m_blackBrush : m_phoneForegroundBrush;

  m_button.Padding = skinned ?
    m_zeroThickness : m_phoneTouchTargetOverhang;

  if (!skinned)
  {
    m_button.Content = null;
  }

  updateSkinnableStateBasedProperties();
}

public bool isSkinned()
{
  bool skinned = false;

  if (m_normalImage != null && m_normalImage.ToString().Length > 0)
  {
    skinned = true;
  }

  return skinned;
}

private void updateSkinnableStateBasedProperties()
{
  if (!m_correctHint && isSkinned())
  {
    m_image.Visibility = Visibility.Visible;

    if (m_pressed && m_pressedImage != null)
    {
      m_image.Source = m_pressedImage;
    }
    else
    {
      m_image.Source = m_normalImage;
    }
  }
  else
  {
    m_image.Source = null;

    if(!m_correctHint)
    {
      m_textbox.Foreground = m_pressed ?
        m_phoneBackgroundBrush : m_phoneForegroundBrush;

      m_button.Background = m_pressed ?
        m_phoneForegroundBrush : m_phoneBackgroundBrush;
    }
  }
}

Answer 1

您可以添加每次Dependency Property更改值时调用的委托......

  public static readonly DependencyProperty NormalImageProperty =
     DependencyProperty.Register(
         NormalImagePropertyTag,
         typeof(ImageSource),
         typeof(CueAnswerViewData),
         new PropertyMetadata(null, (s, e) =>
                var ctrl = s as CueAnswerViewData;
                if (ctrl != null) {
                   ctrl.somePropertyToUpdate = 123;
                }
            })
            );

Answer 2

给Jeff Brand +1，因为他的答案帮助我找到了解决方案。但是，解决此问题的最佳方法是停止尝试对抗系统并将updateSkinnableProperties（）逻辑移动到ViewModel本身，并让它实现INotifyPropertyChanged。它暴露的一些属性更多以UI为中心，而不是以数据为中心（如画笔和厚度属性），但最终这是最干净，最好的解决方案。

谢谢！

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