WPF TreeView BringIntoViewBehavior

由於專案需要，需要能夠定位TreeView中的點，TreeView的節點數過多的情況下，即使找到了對應的節點並選中展示了，由於不在可視區域內，給使用者的感覺還是不好，因此設計如下的Behavior，來實現選中的TreeViewItem顯示在可見區域：

using System;
using System.Windows;
using System.Windows.Controls;

namespace Johar.Core
{
    public static class BringIntoViewBehavior
    {
        public static bool GetIsBringIntoViewWhenSelected(DependencyObject obj)
        {
            return (bool)obj.GetValue(IsBringIntoViewWhenSelectedProperty);
        }

        public static void SetIsBringIntoViewWhenSelected(DependencyObject obj, bool value)
        {
            obj.SetValue(IsBringIntoViewWhenSelectedProperty, value);
        }

        // Using a DependencyProperty as the backing store for IsBringIntoViewWhenSelected.  This enables animation, styling, binding, etc...
        public static readonly DependencyProperty IsBringIntoViewWhenSelectedProperty =
            DependencyProperty.RegisterAttached("IsBringIntoViewWhenSelected", 
            typeof(bool), typeof(BringIntoViewBehavior), 
            new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnIsBringIntoViewWhenSelected)));

        private static void OnIsBringIntoViewWhenSelected(DependencyObject d, DependencyPropertyChangedEventArgs e)
        {
            TreeViewItem item = d as TreeViewItem;
            if (item == null)
            {
                return;
            }

            if (e.NewValue is bool == false)
            {
                return;
            }

            if ((bool)e.NewValue)
            {
                item.Selected -= item_Selected;
                item.Selected += item_Selected;
            }
            else
            {
                item.Selected -= item_Selected;
            }
        }

        private static void item_Selected(object sender, RoutedEventArgs e)
        { 
            TreeViewItem item = e.OriginalSource as TreeViewItem;
            if (item != null)
            {
                item.BringIntoView();
            }
        }
    }
}

然後在TreeView中設定一下這個依賴屬性為True即可上述要求。