具有可绑定选定项的多选列表框DP未绑定回源

请参考以下示例代码。

public class MultipleSelectionListBox : ListBox
{
    public static readonly DependencyProperty BindableSelectedItemsProperty =
        DependencyProperty.Register("BindableSelectedItems",
            typeof(IEnumerable<dynamic>), typeof(MultipleSelectionListBox),
            new FrameworkPropertyMetadata(default(IEnumerable<dynamic>),
                FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnBindableSelectedItemsChanged));

    public IEnumerable<dynamic> BindableSelectedItems
    {
        get => (IEnumerable<dynamic>)GetValue(BindableSelectedItemsProperty);
        set => SetValue(BindableSelectedItemsProperty, value);
    }

    protected override void OnSelectionChanged(SelectionChangedEventArgs e)
    {
        base.OnSelectionChanged(e);
        BindableSelectedItems = SelectedItems.Cast<dynamic>();
    }

    private static void OnBindableSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is MultipleSelectionListBox listBox)
        {
            List<dynamic> newSelection = new List<dynamic>();
            if (!string.IsNullOrWhiteSpace(listBox.SelectedValuePath))
                foreach (var item in listBox.BindableSelectedItems)
                {
                    var collectionValue = item.GetType().GetProperty(listBox.SelectedValuePath).GetValue(item, null);
                    foreach (var lbItem in listBox.Items)
                    {
                        if (lbItem.GetType().GetProperty(listBox.SelectedValuePath).GetValue(lbItem, null) == collectionValue)
                            newSelection.Add(lbItem);
                    }
                }
            else
                newSelection = listBox.BindableSelectedItems as List<dynamic>;

            listBox.SetSelectedItems(listBox.BindableSelectedItems);
        }
    }
}

视图模型:

public class ViewModel : INotifyPropertyChanged
{
    public ViewModel()
    {
        //select 1 and 4 initially:
        MyCollectionOfSelectedIDs = new List<dynamic> { Items[0], Items[3] };
    }

    public IList<DeviceChannelInfo> Items { get; } = new List<DeviceChannelInfo>()
    {
        new DeviceChannelInfo{ name = "1", displayName = "1", id =1 },
        new DeviceChannelInfo{ name = "2", displayName = "2", id =2 },
        new DeviceChannelInfo{ name = "3", displayName = "3", id =3 },
        new DeviceChannelInfo{ name = "4", displayName = "4", id =4 }
    };

    private IEnumerable<dynamic> _mCollectionOfSelectedIDs;
    public IEnumerable<dynamic> MyCollectionOfSelectedIDs
    {
        get { return _mCollectionOfSelectedIDs; }
        set { _mCollectionOfSelectedIDs = value; NotifyPropertyChanged(); }
    }

    public event PropertyChangedEventHandler PropertyChanged;
    private void NotifyPropertyChanged([CallerMemberName] String propertyName = "") =>
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}

<Window x:Class="WpfApp1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp4"
        mc:Ignorable="d"
        Title="MainWindow" Height="300" Width="300">
    <Window.DataContext>
        <local:ViewModel />
    </Window.DataContext>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <local:MultipleSelectionListBox ItemsSource="{Binding Items}" 
                                        SelectionMode="Extended"
                                        DisplayMemberPath="displayName"
                                        SelectedValuePath="name" 
                                        BindableSelectedItems="{Binding MyCollectionOfSelectedIDs}" />

        <TextBlock Grid.Row="1" Text="{Binding MyCollectionOfSelectedIDs.Count}" />
    </Grid>
</Window>

我打碎了这个鸡蛋。

对我来说,最重要的是避免使用行为或代码,我相信我已经完成了这项工作(可能需要一些测试,但到目前为止仍在工作)

public class MultipleSelectionListBox : ListBox
{
    internal bool processSelectionChanges = false;

    public static readonly DependencyProperty BindableSelectedItemsProperty =
        DependencyProperty.Register("BindableSelectedItems",
            typeof(object), typeof(MultipleSelectionListBox),
            new FrameworkPropertyMetadata(default(ICollection<object>),
                FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, OnBindableSelectedItemsChanged));

    public dynamic BindableSelectedItems
    {
        get => GetValue(BindableSelectedItemsProperty);
        set => SetValue(BindableSelectedItemsProperty, value);
    }


    protected override void OnSelectionChanged(SelectionChangedEventArgs e)
    {
        base.OnSelectionChanged(e);

        if (BindableSelectedItems == null || !this.IsInitialized) return; //Handle pre initilized calls

        if (e.AddedItems.Count > 0)
            if (!string.IsNullOrWhiteSpace(SelectedValuePath))
            {
                foreach (var item in e.AddedItems)
                    if (!BindableSelectedItems.Contains((dynamic)item.GetType().GetProperty(SelectedValuePath).GetValue(item, null)))
                        BindableSelectedItems.Add((dynamic)item.GetType().GetProperty(SelectedValuePath).GetValue(item, null));
            }
            else
            {
                foreach (var item in e.AddedItems)
                    if (!BindableSelectedItems.Contains((dynamic)item))
                        BindableSelectedItems.Add((dynamic)item);
            }

        if (e.RemovedItems.Count > 0)
            if (!string.IsNullOrWhiteSpace(SelectedValuePath))
            {
                foreach (var item in e.RemovedItems)
                    if (BindableSelectedItems.Contains((dynamic)item.GetType().GetProperty(SelectedValuePath).GetValue(item, null)))
                        BindableSelectedItems.Remove((dynamic)item.GetType().GetProperty(SelectedValuePath).GetValue(item, null));
            }
            else
            {
                foreach (var item in e.RemovedItems)
                    if (BindableSelectedItems.Contains((dynamic)item))
                        BindableSelectedItems.Remove((dynamic)item);
            }
    }

    private static void OnBindableSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        if (d is MultipleSelectionListBox listBox)
        {
            List<dynamic> newSelection = new List<dynamic>();
            if (!string.IsNullOrWhiteSpace(listBox.SelectedValuePath))
                foreach (var item in listBox.BindableSelectedItems)
                {
                    foreach (var lbItem in listBox.Items)
                    {
                        var lbItemValue = lbItem.GetType().GetProperty(listBox.SelectedValuePath).GetValue(lbItem, null);
                        if ((dynamic)lbItemValue == (dynamic)item)
                            newSelection.Add(lbItem);
                    }
                }
            else
                newSelection = listBox.BindableSelectedItems as List<dynamic>;

            listBox.SetSelectedItems(newSelection);
        }
    }
}