作为绑定目标的属性不更新值

Question

我试图用"IsSelected“属性扩展wpf按钮。我创建了一个依赖项对象，其属性如下所示：

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());
    }
}

我想要对属性进行修改的按钮由ItemsControl生成：

 <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>

​

现在的问题是，将我的视图模型中的"Selected“属性绑定到所访问的属性上。如果我使用的是静态值，那么可以正确地调用属性的"SelectionChanged“均数。

我一装上装订，就什么也没发生。(初始值已正确设置，但更改后的值不被识别。)

静态值

local:FormSelectorExtension.IsSelected="True"

绑定

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

我更新视图模型的代码：

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

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

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

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

假设FrameSelectors是ButtonData实例的集合，那么您也必须在ButtonData类上实现INotifyPropertyChanged：

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

    ...
}

请注意，您的FormSelectorExtension类不需要从DependencyObject派生。这只对常规依赖属性是必需的，而对于附加属性则不是必需的。