如何知道绑定何时更新依赖属性

Question

我正在创建一个具有依赖属性的自定义控件，我希望将自定义类绑定到该控件。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 
}

我绑定到我的属性就好了：

<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"/>

PropertyChangedCallback 只被调用一次，不再调用该方法来更新控件；但是，绑定正在更新，并且当源更新时，属性也会更新...在我的视图模型中也不会调用 onpropertychanged()。

当我通过重新实例化绑定到我的控件的对象来强制在我的视图模型中调用 onpropertychanged() 时 - 绑定工作一次，但当属性更改时它不会更新，即使 onpropertychanged() 正在被调用。

我应该如何知道绑定何时更新？我的依赖属性代码是否正确？

Answer 1

那里有一些我觉得不对劲的地方。

1 这不是必需的，因为绑定会为您执行此操作。如果在此处设置断点，您应该会看到 dayView.Collection 和 e.NewValue 已经相同。

dayView.Collection = e.NewValue as AppointmentCollections;

2 这也不是必需的。我认为这可能是罪魁祸首，因为您将 DataContext 更改为“DayOneAppointmentCollections”不再存在的位置。

dayView.DataContext = dayView.Collection;

3 在 SetupControl 中，请务必取消订阅旧集合。