处理UserControl属性的正确方法？

Question

在我的Windows应用商店中，我有一个CueAnswerButton用户控件。它包含一个Image控件，该控件绑定到视图模型中的{Binding NormalImage}。然而，在CueAnswerButton中有其他控件和属性，当绑定属性发生变化时（我想在CueAnswerButton内部执行代码时，只要它发生变化）就需要更新它们。

我该怎么做？

我发现other articles可以解释类似的情况，但并不完全。也许我不知道使用正确的术语来找到答案。

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，我想打电话给CueAnswerButton.updateSkinnableProperties（）每当在ViewData的变化NormalImage财产。是的，这是一个WP7应用程序的端口:)，它仍然是一个正在进行的工作。

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

给予+ 1名的杰夫品牌，他的回答帮我找到了我的解决方案。然而，解决这个问题的最好方法是停止尝试打击系统并将updateSkinnableProperties（）逻辑移入ViewModel本身，并使其实现INotifyPropertyChanged。它公开的一些属性更多的是以UI为中心而不是以数据为中心的属性（比如Brush和Thickness属性），但最终这是最干净和最好的解决方案。

谢谢！

Answer 2

您可以添加一个被调用的每次改变DependecyProperty值代表...

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; 
       } 
      }) 
      );