ListBox相关的内存泄露

Question

我创建了一个用户控件GroupControl，有AddGroup(object header, object[] items)方法。这个方法就是创建一个GroupBox，设置Header和GroupBox里面的ListBox.ItemsSource。

<ContentControl x:Class="Gqqnbig.TranscendentKill.GroupControl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d" d:DesignHeight="300" d:DesignWidth="300">
    <ItemsControl Name="selectionGroupPanel" x:FieldModifier="private" HorizontalAlignment="Left" VerticalAlignment="Top"/>
</ContentControl>

    public partial class GroupControl
    {
        public GroupControl()
        {
            InitializeComponent();
        }

        public event SelectionChangedEventHandler SelectionChanged;

        public void AddGroup(object header, object[] items)
        {
            GroupBox groupBox = new GroupBox();
            groupBox.Header = header;
            ListBox listBox = new ListBox();
            listBox.ItemsSource = items;
            listBox.SelectionChanged += listBox_SelectionChanged;
            groupBox.Content = listBox;

            selectionGroupPanel.Items.Add(groupBox);
        }

        void listBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (SelectionChanged != null)
                SelectionChanged(this, e);
        }
    }

然后主窗口使用这个GroupControl，在窗口加载的时候往GroupControl里填数据，当用户选择GroupControl里任意一项的时候，卸载这个GroupControl。

代码稍显繁琐，因为这是从我的真实项目中抽取出来用来演示问题的。

    internal partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }


        private void Window_Loaded_1(object sender, RoutedEventArgs e)
        {
            Tuple<string, object[]>[] cps = new Tuple<string, object[]>[2];
            cps[0] = new Tuple<string, object[]>("时间", new[] { (object)DateTime.Now.ToShortTimeString() });
            cps[1] = new Tuple<string, object[]>("日期", new[] { (object)DateTime.Now.ToShortDateString() });


            GroupControl win = new GroupControl();

            for (int i = 0; i < cps.Length; i++)
            {
                ContentPresenter[] items = new ContentPresenter[cps[i].Item2.Length];

                for (int j = 0; j < cps[i].Item2.Length; j++)
                    items[j] = new ContentPresenter { Content = cps[i].Item2[j] };

                win.AddGroup(cps[i].Item1, items);
            }

            win.SelectionChanged += win_SelectionChanged;
            Content = win;
        }

        void win_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            GroupControl win = (GroupControl)this.Content;
            win.SelectionChanged -= win_SelectionChanged;

            Content = null;


            GC.Collect();
        }
    }

<Window x:Class="Gqqnbig.TranscendentKill.UI.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Width="800" x:ClassModifier="internal" Loaded="Window_Loaded_1">

</Window>

当卸载了GroupControl之后，尽管也调用了GC，我用.NET Memory Profiler查看，发现它还是存在。

上图表示GroupBox._contextStorage保存了我的GroupControl；ListBox._parent保存了前面的GroupBox; ItemsPresenter保存了前面的ListBox；以此类推。因为有对GroupControl的引用链存在，所以它无法被垃圾回收。

从前几行来看，都是GroupControl和ListBox、ListBoxItem等的相互引用，这个不成问题。我觉得可能是ListCollectionView跟外部做了什么交互，被引用上了，导致一连串都不能被回收。

能否请各位大侠解释一下这种现象，并请问如何切断这个引用链，让GroupControl能被回收呢？