如何将一个`DependenyProperty`绑定到另一个可附加的`DependencyProperty`？

Question

我想拥有一个持有一些值的单身人士S1和S2我可以绑定到。目标是在其值更改时更新一些UIElements。问题是我想使用重用的DataTemplate中的值。这意味着我不能直接绑定到单例的依赖属性，但必须在外部设置。

要正确传递更新，值必须是DependencyProperty。因为我不知道我必须绑定哪个属性，所以我创建了另一个与数值相同类型的可附加属性AttProperty。现在，我试图绑定S1到AttProperty但是这给了我一个错误：

Additional information: A 'Binding' cannot be set on the 'SetAttProperty' property of type 'TextBox'. A 'Binding' can only be set on a DependencyProperty of a DependencyObject.

那么，如何可以绑定可连接DependencyProperty另一个DependencyProperty？

下面是单身我到目前为止（C＃）代码：

public class DO : DependencyObject 
{ 
    // Singleton pattern (Expose a single shared instance, prevent creating additional instances) 
    public static readonly DO Instance = new DO(); 
    private DO() { } 
    public static readonly DependencyProperty S1Property = DependencyProperty.Register(
    "S1", typeof(string), typeof(DO), 
    new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender)); 
    public string S1 
    { 
    get { return (string)GetValue(S1Property); } 
    set { SetValue(S1Property, value); } 
    } 
    public static readonly DependencyProperty AttProperty = DependencyProperty.RegisterAttached( 
    "Att", typeof(string), typeof(DO), 
    new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender)); 
    public static void SetAttProperty(DependencyObject depObj, string value) 
    { 
    depObj.SetValue(AttProperty, value); 
    } 
    public static string GetAttProperty(DependencyObject depObj) 
    { 
    return (string)depObj.GetValue(AttProperty); 
    } 
} 

这里是有问题的东西（XAML）：

<TextBox Name="Input" Text="" TextChanged="Input_TextChanged" local:DO.AttProperty="{Binding Source={x:Static local:DO.Instance}, Path=S1}" /> 

更新

随着博金利的变化错误消失了。但是，一个问题仍然是 - 如果我现在尝试用这样的附加属性的帮助来更新单：

<TextBox local:DO.Att="{Binding Source={x:Static local:DO.Instance}, Path=S1, Mode=TwoWay}" Text="{Binding Path=(local:DO.Att), RelativeSource={RelativeSource Self}, Mode=TwoWay}"/> 

为什么不值在单传播到S1？

Answer 1

您需要执行INotifyPropertyChanged和电线的变化到依赖属性变化。

public class DO : DependencyObject,INotifyPropertyChanged { 
     // Singleton pattern (Expose a single shared instance, prevent creating additional instances) 
     public static readonly DO Instance = new DO(); 
     private DO() { } 
     public static readonly DependencyProperty S1Property = DependencyProperty.Register(
      "S1", typeof(string), typeof(DO), 
      new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender,onS1Changed)); 

     private static void onS1Changed(DependencyObject d, DependencyPropertyChangedEventArgs e) { 
      DO item = d as DO; 
      if (item != null) item.OnPropertyChanged(new PropertyChangedEventArgs("S1")); 
     } 

     public string S1 { 
      get { return (string)GetValue(S1Property); } 
      set { SetValue(S1Property, value); } 
     } 
     public static readonly DependencyProperty AttProperty = DependencyProperty.RegisterAttached(
      "Att", typeof(string), typeof(DO), 
      new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender,onAttChanged)); 

     private static void onAttChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { 
      DO item = d as DO; 
      if (item != null) item.OnPropertyChanged(new PropertyChangedEventArgs("Att")); 
     } 

     public static void SetAttProperty(DependencyObject depObj, string value) { 
      depObj.SetValue(AttProperty, value); 
     } 
     public static string GetAttProperty(DependencyObject depObj) { 
      return (string)depObj.GetValue(AttProperty); 
     } 

     public event PropertyChangedEventHandler PropertyChanged; 

     public void OnPropertyChanged(PropertyChangedEventArgs e) { 
      PropertyChangedEventHandler handler = PropertyChanged; 
      if (handler != null) handler(this, e); 
     } 
    } 

Answer 2

我不认为您正确指定了您的附加属性的Get/Set访问器，如记录here。试试这个：

public static readonly DependencyProperty AttProperty = DependencyProperty.RegisterAttached(
     "Att", typeof(string), typeof(DO), 
     new FrameworkPropertyMetadata(null, FrameworkPropertyMetadataOptions.AffectsRender)); 
    public static void SetAtt(DependencyObject depObj, string value) 
    { 
     depObj.SetValue(AttProperty, value); 
    } 
    public static string GetAtt(DependencyObject depObj) 
    { 
     return (string)depObj.GetValue(AttProperty); 
    } 

实例绑定：

<TextBlock local:DO.Att="{Binding Source={x:Static local:DO.Instance}, Path=S1}" Text="{Binding Path=(local:DO.Att),RelativeSource={RelativeSource Self}}">