WPF 保持 TreeView 列表排序

如何使用WPF保持TreeView列表排序

csharp
using System.Collections;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
public class SortedTreeView : TreeView
{
    public static readonly DependencyProperty SortModeProperty =
        DependencyProperty.Register("SortMode", typeof(SortMode), typeof(SortedTreeView), new PropertyMetadata(SortMode.Ascending, OnSortModeChanged));
    public SortMode SortMode
    {
        get { return (SortMode)GetValue(SortModeProperty); }
        set { SetValue(SortModeProperty, value); }
    }
    private static void OnSortModeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var treeView = (SortedTreeView)d;
        treeView.SortItems();
    }
    protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
    {
        base.OnItemsChanged(e);
        SortItems();
    }
    private void SortItems()
    {
        var view = CollectionViewSource.GetDefaultView(ItemsSource);
        if (view != null)
        {
            view.SortDescriptions.Clear();
            view.SortDescriptions.Add(new SortDescription("Header", SortMode == SortMode.Ascending ? ListSortDirection.Ascending : ListSortDirection.Descending));
        }
    }
}
public enum SortMode
{
    Ascending,
    Descending
}

xaml