Question

我正在创建一个带有依赖项属性的自定义控件，我希望将自定义类绑定到该属性。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，从不再次调用该方法来更新控件;然而，绑定正在更新，当源更新时，属性会更新...也不会在我的viewmodel中调用onpropertychanged（）。

当我通过重新实例化绑定到我的控件的对象强制在我的viewmodel中调用onpropertychanged（）时 - 绑定工作一次，但即使调用了onpropertychanged（），它也不会在属性更改时更新。

我怎么知道绑定更新的时间？我的dependencyproperty代码是否正确？

Answer 1

有一些事情对我来说是错误的。

1这不是必需的，因为绑定会为您做到这一点。如果你在这里放一个断点，你应该看到dayView.Collection和e.NewValue已经相同了。

dayView.Collection = e.NewValue as AppointmentCollections;

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

dayView.DataContext = dayView.Collection;

3在SetupControl中，请务必取消订阅旧收藏。

如何知道何时绑定已在依赖项属性上更新

1 个答案: