WPF集合多绑定问题：控件随其他控件可见子项自动隐藏失效

我完全理解你的需求——想让Button在ListBox没有可见子项时自动隐藏。你的思路方向是对的，但当前实现的BindingExpander转换器存在关键问题，导致集合更新时绑定无法重新求值：

为什么你的当前代码不生效？ #

• 你通过BindingExpander返回一个List<Binding>给MultiBinding，但MultiBinding并不会动态监听这些生成的绑定，也不会在ListBox的Items集合内部元素增减时重新调用BindingExpander的Convert方法（因为Items集合的引用本身没变，只是内部元素变了，默认绑定只会响应属性引用变化）。
• 即使Items集合更新，TestConverter也无法感知到子项Visibility的变化，因为它只在初始化时获取一次值。

推荐解决方案：使用Behavior实现解耦的监听 #

最优雅的方式是用WPF行为（Behavior）来实现，它能自动监听Items集合的变化和每个子项的Visibility状态，逻辑清晰且可复用。

步骤1：创建自定义Behavior

首先安装NuGet包Microsoft.Xaml.Behaviors.Wpf，然后编写行为类：

using Microsoft.Xaml.Behaviors;
using System.Collections.Specialized;
using System.Windows;
using System.Windows.Controls;
using System.ComponentModel;

namespace YourNamespace
{
    public class HideWhenNoVisibleItemsBehavior : Behavior<FrameworkElement>
    {
        public static readonly DependencyProperty TargetControlProperty =
            DependencyProperty.Register("TargetControl", typeof(FrameworkElement), typeof(HideWhenNoVisibleItemsBehavior), new PropertyMetadata(null));

        public FrameworkElement TargetControl
        {
            get => (FrameworkElement)GetValue(TargetControlProperty);
            set => SetValue(TargetControlProperty, value);
        }

        private ItemsControl _itemsControl;

        protected override void OnAttached()
        {
            base.OnAttached();
            _itemsControl = AssociatedObject as ItemsControl;
            if (_itemsControl == null) return;

            // 监听Items集合的增减
            if (_itemsControl.Items is INotifyCollectionChanged collection)
                collection.CollectionChanged += ItemsCollectionChanged;

            // 监听现有子项的Visibility变化
            foreach (var item in _itemsControl.Items)
                RegisterContainerListener(item);

            // 监听新生成的子项容器
            _itemsControl.ItemContainerGenerator.StatusChanged += GeneratorStatusChanged;

            UpdateTargetVisibility();
        }

        protected override void OnDetaching()
        {
            base.OnDetaching();
            if (_itemsControl == null) return;

            if (_itemsControl.Items is INotifyCollectionChanged collection)
                collection.CollectionChanged -= ItemsCollectionChanged;

            foreach (var item in _itemsControl.Items)
                UnregisterContainerListener(item);

            _itemsControl.ItemContainerGenerator.StatusChanged -= GeneratorStatusChanged;
        }

        private void GeneratorStatusChanged(object sender, EventArgs e)
        {
            if (_itemsControl.ItemContainerGenerator.Status == System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated)
            {
                foreach (var item in _itemsControl.Items)
                    RegisterContainerListener(item);
                UpdateTargetVisibility();
            }
        }

        private void ItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
        {
            if (e.NewItems != null)
                foreach (var item in e.NewItems)
                    RegisterContainerListener(item);

            if (e.OldItems != null)
                foreach (var item in e.OldItems)
                    UnregisterContainerListener(item);

            UpdateTargetVisibility();
        }

        private void RegisterContainerListener(object item)
        {
            if (_itemsControl.ItemContainerGenerator.ContainerFromItem(item) is FrameworkElement container)
            {
                DependencyPropertyDescriptor.FromProperty(UIElement.VisibilityProperty, typeof(FrameworkElement))
                    .AddValueChanged(container, OnContainerVisibilityChanged);
            }
        }

        private void UnregisterContainerListener(object item)
        {
            if (_itemsControl.ItemContainerGenerator.ContainerFromItem(item) is FrameworkElement container)
            {
                DependencyPropertyDescriptor.FromProperty(UIElement.VisibilityProperty, typeof(FrameworkElement))
                    .RemoveValueChanged(container, OnContainerVisibilityChanged);
            }
        }

        private void OnContainerVisibilityChanged(object sender, EventArgs e)
        {
            UpdateTargetVisibility();
        }

        private void UpdateTargetVisibility()
        {
            if (TargetControl == null || _itemsControl == null) return;

            bool hasVisibleItems = _itemsControl.Items
                .Select(item => _itemsControl.ItemContainerGenerator.ContainerFromItem(item) as FrameworkElement)
                .Any(container => container?.Visibility == Visibility.Visible);

            TargetControl.Visibility = hasVisibleItems ? Visibility.Visible : Visibility.Collapsed;
        }
    }
}

步骤2：在XAML中使用Behavior

<Window xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
        xmlns:local="clr-namespace:YourNamespace"
        Title="MainWindow" Height="450" Width="800">
    <Grid>
        <Button x:Name="btnToHide" 
                Content="Button" 
                HorizontalAlignment="Left" 
                Margin="237,166,0,0" 
                VerticalAlignment="Top" 
                Width="75" 
                Click="Button_Click"/>
        
        <ListBox x:Name="lstItems" 
                 HorizontalAlignment="Left" 
                 Height="100" 
                 Margin="601,130,0,0" 
                 VerticalAlignment="Top" 
                 Width="100" 
                 DisplayMemberPath="Content">
            <i:Interaction.Behaviors>
                <!-- 将Behavior附加到ListBox，并指定要控制的目标Button -->
                <local:HideWhenNoVisibleItemsBehavior TargetControl="{Binding ElementName=btnToHide}"/>
            </i:Interaction.Behaviors>
        </ListBox>
    </Grid>
</Window>

方案优势 #

• 自动监听Items集合的增减，以及每个子项的Visibility变化，实时更新目标控件状态
• 完全解耦，Behavior可以复用在任何ItemsControl和目标控件组合上
• 有完整的生命周期管理，不会出现内存泄漏问题

内容的提问来源于stack exchange，提问作者Tony Valenti