作爲綁定目標的Attatched屬性不更新值

Question

我試圖用「IsSelected」屬性擴展wpf按鈕。我創建了一個依賴的對象與attatched屬性看起來像這樣：

class FormSelectorExtension : DependencyObject 
{ 
    public static DependencyProperty IsSelectedProperty = 
     DependencyProperty.RegisterAttached("IsSelected", typeof(bool), typeof(FormSelectorExtension), 
     new PropertyMetadata(new PropertyChangedCallback(SelectionChanged))); 

    public static bool GetIsSelected(DependencyObject obj) 
    { 
     return (bool)obj.GetValue(IsSelectedProperty); 
    } 

    public static void SetIsSelected(DependencyObject obj, bool value) 
    { 
     obj.SetValue(IsSelectedProperty, value); 
    } 

    private static void SelectionChanged(DependencyObject obj, DependencyPropertyChangedEventArgs e) 
    { 
     Console.WriteLine(obj.ToString()); 
    } 
} 

我想attatch到由一個ItemsControl生成的屬性按鈕：現在

<ItemsControl x:Name="frameSelector" ItemsSource="{Binding Path=FrameSelectors}" Grid.Column="2" Grid.RowSpan="2" Width="150" VerticalContentAlignment="Stretch" HorizontalAlignment="Stretch"> 
<ItemsControl.ItemsPanel> 
    <ItemsPanelTemplate> 
     <UniformGrid Columns="1"/> 
    </ItemsPanelTemplate> 
</ItemsControl.ItemsPanel> 
<ItemsControl.ItemTemplate> 
    <DataTemplate> 
     <Button Content="{Binding Path=DisplayName}" Command="{Binding Path=ButtonCommand}" CommandParameter="{Binding Path=CommandParameter}" 
       Style="{StaticResource ResourceKey=FrameSelectorStyle}" FontSize="28" local:FormSelectorExtension.IsSelected="{Binding Path=Selected}"/> 
    </DataTemplate> 
</ItemsControl.ItemTemplate> 

的問題，是我的視圖模型的「Selected」屬性與attatched屬性的綁定。如果我使用靜態值，則可以正確調用attatched屬性的「SelectionChanged」事件處理程序。

只要我把綁定，沒有任何反應。 （初始值設置正確，但改變不承認。）

靜態值

local:FormSelectorExtension.IsSelected="True" 

綁定

local:FormSelectorExtension.IsSelected="{Binding Path=Selected}" 

的代碼，我更新我的視圖模型：

private void ActivateFrame(FormsFrame selectedFrame) 
{ 
    ActiveFrame = selectedFrame;  

    foreach(var selector in FrameSelectors) 
     selector.Selected = selector.DisplayName == selectedFrame.DisplayName; 

    OnPropertyChanged("FrameSelectors"); 
    OnPropertyChanged("ActiveFrame"); 
} 

和我的ViewModel：

public class ButtonData 
{ 
    public String DisplayName { get; set; } 
    public bool Selected { get; set; } 

    public ICommand ButtonCommand { get; set; } 
    public object CommandParameter { get; set; } 
} 

Answer 1

假設FrameSelectors是ButtonData實例的集合，你將不得不對ButtonData類實現INotifyPropertyChanged太：

public class ButtonData : INotifyPropertyChanged 
{ 
    private bool selected; 
    public bool Selected 
    { 
     get { return selected; } 
     set 
     { 
      selected = value; 
      OnPropertyChanged("Selected"); 
     } 
    } 

    ... 
} 

---

作爲一個說明，你FormSelectorExtension類並不需要派生來自DependencyObject。這隻對常規的依賴項屬性是必需的，對於附屬屬性則不是。