WPF。将列表框项模板内部绑定到 ObservableCollection 源。 Source PropertyChanged 被忽略

Question

我正在尝试创建一个显示格式化文本的列表框。 我希望能够从代码更改格式。

为了显示格式化文本，我选择了 TextBlock 并打算使用 TextBlock.Inlines 集合进行格式化。 TextBlock.Inlines 不可绑定，因此我创建了从 TextBlock 派生的新 class BindableTextBlock 。 这个 class 有一个依赖属性InlineList ，我试图将其绑定到Model 中的 InlinesColl ObservableCollection。

问题是InlinesColl中的更改不会将 PropertyChanged 事件通知我的InlineList 。 绑定仅在BindableTextBlock object 创建时运行一次，此后便不再运行。

任何想法为什么？

XAML：

                <ListBox  x:Name="PART_lb" VerticalAlignment="Stretch" ItemsSource="{Binding ItemColl}"
                            ScrollViewer.HorizontalScrollBarVisibility="Auto" 
                            ScrollViewer.VerticalScrollBarVisibility="Auto" >
                    
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <local:BindableTextBlock InlineList="{Binding Path=InlinesColl}" />
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                    
                </ListBox>

可绑定文本块 class：

 public class BindableTextBlock : TextBlock
    {
        public ObservableCollection<Inline> InlineList
        {
            get { return (ObservableCollection<Inline>)GetValue(InlineListProperty); }
            set { SetValue(InlineListProperty, value); }
        }

        public static readonly DependencyProperty InlineListProperty =
            DependencyProperty.Register("InlineList", typeof(ObservableCollection<Inline>), typeof(BindableTextBlock), new UIPropertyMetadata(null, OnPropertyChanged));

        private static void OnPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            BindableTextBlock textBlock = (BindableTextBlock)sender;
            textBlock.Inlines.Clear();
            textBlock.Inlines.AddRange((ObservableCollection<Inline>)e.NewValue);
        }

      
    }

Model class

    public class TextBlockModel
    {

        ObservableCollection<Inline> _inlinesColl = new ObservableCollection<Inline>();
        public ObservableCollection<Inline> InlinesColl
        {
            get { return _inlinesColl; }
            set {_inlinesColl = value; }
        }
    }

带有 ListBox ItemSource 集合的 ViewModel

        ObservableCollection<TextBlockModel> _itemColl = new ObservableCollection<TextBlockModel>();
        public ObservableCollection<TextBlockModel> ItemColl
        {
            get { return _itemColl; }
            set { _itemColl = value; }
        }

在这里测试项目

Answer 1

在你的情况下 - 你没有处理集合中的项目添加\删除的情况
需要 go 并在分配新集合时订阅 CollectionChanged。

 public class BindableTextBlock : TextBlock
    {
        static int Cntr = 0;
        public BindableTextBlock()
        {
            Console.WriteLine("BindableTextBlock constructor " + Cntr);
            Cntr++;
        }

        public ObservableCollection<Inline> InlineList
        {
            get { return (ObservableCollection<Inline>)GetValue(InlineListProperty); }
            set { SetValue(InlineListProperty, value); }
        }

        public static readonly DependencyProperty InlineListProperty =
            DependencyProperty.Register("InlineList", typeof(ObservableCollection<Inline>), typeof(BindableTextBlock), new UIPropertyMetadata(null, OnPropertyChanged));

        private static void OnPropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            BindableTextBlock textBlock = (BindableTextBlock)sender;

            // subscribe to collection changed
            textBlock.UpdateInlineListSource((ObservableCollection < Inline > )e.OldValue, (ObservableCollection < Inline > )e.NewValue);

        }

        public void UpdateInlineListSource(ObservableCollection<Inline> oldCollection, ObservableCollection<Inline> newCollection)
        {
            if (oldCollection!=null)
            oldCollection.CollectionChanged -= OnCollectionChanged;

            if (newCollection != null)
            {
                newCollection.CollectionChanged += OnCollectionChanged;
                OnCollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
                OnCollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, newCollection));
            }
        }

        private void OnCollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
        {
            var newItems = e.NewItems?.Cast<Inline>()?.ToList() ?? new List<Inline>();
            var oldItems = e.OldItems?.Cast<Inline>()?.ToList() ?? new List<Inline>();

            // changed source
            if (e.Action==NotifyCollectionChangedAction.Reset)
                this.Inlines.Clear();

            foreach (var itemForDelete in oldItems)
            {
                if (this.Inlines.Contains(itemForDelete))
                    this.Inlines.Remove(itemForDelete);
            }

            foreach (var itemsForAdd in newItems)
            {
                this.Inlines.Add(itemsForAdd);
            }
        }
    }