protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
 {
     if (_IsUpdate)
     {
         return;
     }
     GUIThreadHelper.Invoke(() => RaiseCollectionChanged(e));
 }
 /// <summary>
 /// 更新集合内容,更新完成后统一通知集合变更。
 /// </summary>
 /// <param name="call"></param>
 public void BeginUpdate(Action call)
 {
     try
     {
         _IsUpdate = true;
         GUIThreadHelper.Invoke(() =>
         {
             call();
             base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
         });
     }
     finally
     {
         _IsUpdate = false;
     }
 }