WPF TreeView BringIntoViewBehavior

因爲項目須要，須要可以定位TreeView中的點，TreeView的節點數過多的狀況下，即便找到了對應的節點並選中展現了，因爲不在可視區域內，給用戶的感受仍是很差，所以設計以下的Behavior，來實現選中的TreeViewItem顯示在可見區域：

 1 using System;
 2 using System.Windows;
 3 using System.Windows.Controls;
 4 
 5 namespace Johar.Core
 6 {
 7     public static class BringIntoViewBehavior
 8     {
 9         public static bool GetIsBringIntoViewWhenSelected(DependencyObject obj)
10         {
11             return (bool)obj.GetValue(IsBringIntoViewWhenSelectedProperty);
12         }
13 
14         public static void SetIsBringIntoViewWhenSelected(DependencyObject obj, bool value)
15         {
16             obj.SetValue(IsBringIntoViewWhenSelectedProperty, value);
17         }
18 
19         // Using a DependencyProperty as the backing store for IsBringIntoViewWhenSelected.  This enables animation, styling, binding, etc...
20         public static readonly DependencyProperty IsBringIntoViewWhenSelectedProperty =
21             DependencyProperty.RegisterAttached("IsBringIntoViewWhenSelected", 
22             typeof(bool), typeof(BringIntoViewBehavior), 
23             new FrameworkPropertyMetadata(false, new PropertyChangedCallback(OnIsBringIntoViewWhenSelected)));
24 
25         private static void OnIsBringIntoViewWhenSelected(DependencyObject d, DependencyPropertyChangedEventArgs e)
26         {
27             TreeViewItem item = d as TreeViewItem;
28             if (item == null)
29             {
30                 return;
31             }
32 
33             if (e.NewValue is bool == false)
34             {
35                 return;
36             }
37 
38             if ((bool)e.NewValue)
39             {
40                 item.Selected -= item_Selected;
41                 item.Selected += item_Selected;
42             }
43             else
44             {
45                 item.Selected -= item_Selected;
46             }
47         }
48 
49         private static void item_Selected(object sender, RoutedEventArgs e)
50         { 
59             TreeViewItem item = e.OriginalSource as TreeViewItem;
60             if (item != null)
61             {
62                 item.BringIntoView();
63             }
64         }
65     }
66 }

而後在TreeView中設置一下這個依賴屬性爲True便可上述要求。