筛选列表框中的组合框

根据@Ed Plunkett的建议，我终于可以使用ComboBox绑定到的代理对象了。这使我可以在触发相关操作（如添加新的列表项或在组合框中选择不同的值）时刷新每个ComboBox的可用项，只需替换每个ComboBoxBindingSource上的AvailableItems属性值。

这也允许XAML更加干净，因为每个ComboBox现在都有一个合适的绑定：

<UserControl x:foobar x:Name="MultiSelectList">
    <Grid>
        <ListBox ItemsSource="{Binding ElementName=MultiSelectList, Path=ComboBoxBindingSources, Mode=TwoWay}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <ComboBox ItemsSource="{Binding Path=AvailableElements}" SelectedValue="{Binding Path=SelectedElement}" SelectionChanged="ComboBox_SelectionChanged" />
                </DataTemplate> 
            </ListBox.ItemTemplate>
        </ListBox>
        <Button Content="New" Click="NewButton_Pressed"/>
    </Grid>
</UserControl>

背后的工作代码是：

  using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
namespace WPFCentralOffice.UserControls
{
    public class Element : IEquatable<Element>
    {
        public int ID { get; set; }
        public string Caption { get; set; }
        public bool Equals(Element other)
        {
            return ID == other.ID;
        }
        public override string ToString()
        {
            return Caption;
        }
    }
    public class ComboBoxBindingSource : INotifyPropertyChanged
    {
        public event PropertyChangedEventHandler PropertyChanged;
        public ComboBoxBindingSource(Element selectedElement, IEnumerable<Element> availableElements)
        {
            _selectedElement = selectedElement;
            AvailableElements = availableElements;
        }
        private Element _selectedElement;
        public Element SelectedElement
        {
            get { return _selectedElement; }
            set
            {
                _selectedElement = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("SelectedElement"));
                }
            }
        }
        private IEnumerable<Element> _availableElements;
        public IEnumerable<Element> AvailableElements
        {
            get { return _availableElements; }
            set
            {
                _availableElements = value;
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs("AvailableElements"));
                }
            }
        }
    }
    public partial class MultiSelectListUserControl : UserControl
    {
        public IEnumerable<Element> ChosenItems
        {
            get { return ComboBoxBindingSources.Select(x => x.SelectedElement); }
        }
        public ObservableCollection<Element> AllItems
        {
            get { return (ObservableCollection<Element>)GetValue(AllItemsProperty); }
            set { SetValue(AllItemsProperty, value); }
        }
        // ReSharper disable once InconsistentNaming
        public ObservableCollection<ComboBoxBindingSource> ComboBoxBindingSources
        {
            get { return (ObservableCollection<ComboBoxBindingSource>)GetValue(ComboBoxBindingSourcesProperty); }
            set { SetValue(ComboBoxBindingSourcesProperty, value); }
        }
        public static DependencyProperty AllItemsProperty = DependencyProperty.Register(
            "AllItems",
            typeof(ObservableCollection<Element>),
            typeof(MultiSelectListUserControl),
            new FrameworkPropertyMetadata(OnAllItemsChanged));
        private static void OnAllItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            ((MultiSelectListUserControl)d).RefreshAvailableItems();
        }
        public static DependencyProperty ComboBoxBindingSourcesProperty = DependencyProperty.Register(
            "ComboBoxBindingSources",
            typeof(ObservableCollection<ComboBoxBindingSource>),
            typeof(MultiSelectListUserControl));
        public void NewButton_Pressed(object sender, RoutedEventArgs e)
        {
            if (!AllItems.Any() || AllItems.Count == ComboBoxBindingSources.Count)
            {
                return;
            }
            var remainingItems = AllItems.Where(x => ChosenItems.All(y => x.ID != y.ID)).ToList();
            ComboBoxBindingSources.Add(new ComboBoxBindingSource(remainingItems.First(), remainingItems));
            RefreshAvailableItems();
        }
        public void ComboBox_SelectionChanged(object sender, RoutedEventArgs e)
        {
            RefreshAvailableItems();
        }
        private void RefreshAvailableItems()
        {
            if (ComboBoxBindingSources == null)
            {
                ComboBoxBindingSources = new ObservableCollection<ComboBoxBindingSource>();
            }
            foreach (var source in ComboBoxBindingSources)
            {
                var newAvailables =
                    AllItems.Where(
                        x => source.SelectedElement == x || ComboBoxBindingSources.All(y => y.SelectedElement != x));
                source.AvailableElements = newAvailables;
            }
        }
        public MultiSelectListUserControl()
        {
            InitializeComponent();
            SetValue(AllItemsProperty, new ObservableCollection<Element>());
        }
    }
}