如何知道何时绑定已更新依赖项属性

Question

我正在创建一个自定义控件，其中包含要绑定自定义类的依赖项属性。当属性得到更新时，我想调用一个方法，以便它可以重新配置控件...我迷路了。

internal partial class CollectionScheduleDayView : Canvas 
    { 
     public static DependencyProperty AppointmentsCollectionProperty = DependencyProperty.Register("Collection", typeof(AppointmentCollections), typeof(CollectionScheduleDayView), new PropertyMetadata(null, PropertyChangedCallback)); 


     private static void PropertyChangedCallback(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e) 
     { 
      SetDataContext(dependencyObject, e); 
     } 

     public AppointmentCollections Collection 
     { 
      get 
      { 
       return GetValue(AppointmentsCollectionProperty) as AppointmentCollections; 
      } 
      set 
      { 
       SetValue(AppointmentsCollectionProperty, value); 
      } 
     } 

     public CollectionScheduleDayView() 
     { 
      InitializeComponent(); 
     } 

     void CollectionScheduleDayView_DataContextChanged(object sender, DependencyPropertyChangedEventArgs e) 
     { 

     } 


     private static void SetDataContext(DependencyObject control, DependencyPropertyChangedEventArgs e) 
     { 
      var dayView = control as CollectionScheduleDayView; 

      if (e.NewValue != null) 
      { 
       if (dayView != null) 
       { 
        dayView.Collection = e.NewValue as AppointmentCollections; 
        dayView.DataContext = dayView.Collection; 
        dayView.SetupControl(); 
       } 
      } 
     } 

     public void SetupControl() 
     { 
      ResetControl(); 

      Collection.RescheduledAppointments.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(RescheduledAppointments_CollectionChanged); 
      Collection.CompletedAppointments.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(CompletedAppointments_CollectionChanged); 
      Collection.RemainingAppointments.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(RemainingAppointments_CollectionChanged); 

      if (Collection.RescheduledAppointments == null || Collection.RescheduledAppointments.Count == 0) 
      { 
       CollapseRescheduled(); 
      } 
      if (Collection.CompletedAppointments == null ||Collection.CompletedAppointments.Count == 0) 
      { 
       CollapseCompleted(); 
      } 
     } 

     //...some other code below 
} 

我绑定到我的财产就好：

<my:CollectionScheduleDayView Grid.Column="0" HorizontalAlignment="Left" Margin="12,35,0,0" x:Name="DayView0" VerticalAlignment="Top" Collection="{Binding DayOneAppointmentCollections, NotifyOnSourceUpdated=True}" SourceUpdated="CollectionScheduleDayView1_OnSourceUpdated"/> 

的PropertyChangedCallback只被调用一次，不会再调用该方法以更新控制;然而，绑定正在更新，当源得到更新时，属性得到更新... onpropertychanged（）不会在我的viewmodel中被调用。

当我强制onpropertychanged（）在我的viewmodel中通过重新实例化绑定到我的控件的对象时调用 - 绑定工作一次，但它不更新时属性更改即使onpropertychanged（）被调用。

我该如何知道绑定更新的时间？我的依赖属性代码是否正确？

Answer 1

有一些东西看起来不对我。

1这是不需要的，因为绑定会为你做。如果你在这里放置一个断点，你应该看到dayView.Collection和e.NewValue已经是相同的了。

dayView.Collection = e.NewValue as AppointmentCollections; 

2这也是没有必要的。我认为这可能是您将DataContext更改为“DayOneAppointmentCollections”不再存在的主要罪魁祸首。

dayView.DataContext = dayView.Collection; 

3在SetupControl中，一定要取消订阅旧集合。