如何在 UserControl 中绑定集合依赖属性

Question

这不是重复的！当我失败时，我试图寻找类似的帖子，但没有成功。我不明白为什么不调用OnUCItemsSourceChanged？我很确定我错过了一些简单的东西，但我找不到它。

我有Window，其中包含UserControl1，它附加了绑定到Window 的WindowCollection 集合的集合属性。我希望在向WindowCollection 添加项目时调用UserControl1.OnUCItemsSourceChanged。但它不会发生。

我想念什么？

Window1.xaml.cs

public partial class Window1 : Window
{
    public ObservableCollection<long> WindowCollection { get; set; }
    public Window1()
    {
        InitializeComponent();

        DataContext = this;

        WindowCollection = new ObservableCollection<long>();
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        WindowCollection.Add(1);
        WindowCollection.Add(2);
    }
}

Window1.xaml

<StackPanel>
    <uc:UserControl1 UCItemsSource="{Binding Path=WindowCollection}" />
    <Button Content="Refresh" Click="Button_Click" />
</StackPanel>

UserControl1.xaml.cs

public static readonly DependencyProperty UCItemsSourceProperty = DependencyProperty.Register("UCItemsSource", typeof(IEnumerable), typeof(UserControl1), new PropertyMetadata(null, new PropertyChangedCallback(OnUCItemsSourceChanged)));

public IEnumerable UCItemsSource
{
    get { return (IEnumerable)GetValue(UCItemsSourceProperty ); }
    set { SetValue(UCItemsSourceProperty , value); }
}

public ObservableCollection<MyItem> UCItems { get; set; }

private static void OnUCItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
    var control = d as UserControl1;
    var items = e.NewValue as ObservableCollection<long>;

    foreach (var item in items)
   {
         control.UCItems.Add(new MyItem(item));
   }
}

UserControl1.xaml

<ItemsControl ItemsSource="{Binding UCItems}" ... />

更新 这是我的测试项目的link

Answer 1

在这一行：

<ItemsControl ItemsSource="{Binding UCItems}" ... />

必须是 RelativeSource 和 FindAncestor，因为 UCItems 位于 UserControl：

UserControl

<ItemsControl ItemsSource="{Binding Path=UCItems,
                                    RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControl}}}" />

---

I cannot understand why OnUCItemsSourceChanged is not called?

如果你添加RelativeSource 构造，那么OnUCItemsSourceChanged 至少会导致一次，因为PropertyChangedCallback 每次都会触发然后你为依赖属性设置新值：

表示依赖属性的有效属性值发生变化时调用的回调。

因为你曾经在这里设置了依赖属性的值：

<uc:UserControl1 UCItemsSource="{Binding Path=WindowCollection}" />

---

I expect UserControl1.OnUCItemsSourceChanged to be called when I add items to WindowCollection.

这是一个ObservableCollection<T>.CollectionChanged 事件，其中包含对集合执行的操作的枚举：

在添加、删除、更改、移动项目或刷新整个列表时发生。

对于您的情况，它将是这样的：

Version with CollectionChanged

MainWindow

public partial class MainWindow : Window
{
    public ObservableCollection<long> WindowCollection { get; set; }

    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;

        WindowCollection = new ObservableCollection<long>();

        WindowCollection.Add(1);
        WindowCollection.Add(2);            
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
        WindowCollection.Add(3);
        WindowCollection.Add(4);
    }
}

UserControl

public partial class UserControl1 : UserControl
{
    #region Public Section

    public ObservableCollection<long> UCItems { get; set; }
    public static UserControl1 control;

    #endregion

    public UserControl1()
    {
        InitializeComponent();
        UCItems = new ObservableCollection<long>();            
    }

    #region UCItemsSource Property

    public static readonly DependencyProperty UCItemsSourceProperty = DependencyProperty.Register("UCItemsSource", 
                                                                                                  typeof(IEnumerable), 
                                                                                                  typeof(UserControl1),
                                                                                                  new PropertyMetadata(null, new PropertyChangedCallback(OnUCItemsSourceChanged)));

    public IEnumerable UCItemsSource
    {
        get { return (IEnumerable)GetValue(UCItemsSourceProperty); }
        set { SetValue(UCItemsSourceProperty, value); }
    }

    #endregion

    private static void OnUCItemsSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        control = d as UserControl1;
        var items = e.NewValue as ObservableCollection<long>;

        items.CollectionChanged += new NotifyCollectionChangedEventHandler(CollectionChanged);
        AddItem(control, items);
    }

    private static void CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        var items = sender as ObservableCollection<long>;
        control.UCItems.Clear();

        if (e.Action == NotifyCollectionChangedAction.Add)
        {
            AddItem(control, items);
        }
    }

    private static void AddItem(UserControl1 userControl, ObservableCollection<long> collection) 
    {
        if (collection.Count > 0)
        {
            foreach (var item in collection)
            {
                userControl.UCItems.Add(item);
            }
        }
    }
}

---

此项目可在此link

Alternative version

这个版本更简单，更正确。这里我们只引用了包含集合的UCItemsSource 属性，这里也是RelativeSource justified：

UserControl

XAML

<Grid>
    <ItemsControl ItemsSource="{Binding Path=UCItemsSource, 
                                        RelativeSource={RelativeSource Mode=FindAncestor,
                                                                       AncestorType={x:Type UserControl}}}">
        <ItemsControl.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding}" />
            </DataTemplate>
        </ItemsControl.ItemTemplate>
    </ItemsControl>
</Grid>

Code-behind

public partial class UserControl1 : UserControl
{
    #region Public Section

    public ObservableCollection<long> UCItems { get; set; }

    #endregion

    public UserControl1()
    {
        InitializeComponent();

        UCItems = new ObservableCollection<long>();
    }

    #region UCItemsSource Property

    public static readonly DependencyProperty UCItemsSourceProperty = DependencyProperty.Register("UCItemsSource", 
                                                                                                  typeof(IEnumerable), 
                                                                                                  typeof(UserControl1));                                                                                                      

    public IEnumerable UCItemsSource
    {
        get { return (IEnumerable)GetValue(UCItemsSourceProperty); }
        set { SetValue(UCItemsSourceProperty, value); }
    }

    #endregion
}

Answer 2

试试这个

private ObservableCollection<long> _windowCollection 
public ObservableCollection<long> WindowCollection 
{ 
   get { return _windowCollection; }
   set
   {
      _windowCollection = value;
      RaiseOnPropertyChange(() => WindowCollection);
   }
}