wpf 虚拟化操作异常

 //Action action = () =>
                //{
                try
                {
                    TreeViewItem itemSelected = null;

                    //Force to generate every treeView item by using scroll item
                    if (virtualizingPanel != null)
                    {
                        try
                        {
                            if (isCallEnd)
                            {
                                isCallEnd = false;
                                virtualizingPanel.CallBringIndexIntoView(selectedIndex);
                                isCallEnd = true;
                            }
                        }
                        catch (System.Exception ex)
                        {
                            Logger.Error("CallBringIndexIntoView exception : ", ex);
                        }

                        itemSelected = (TreeViewItem)_currentSelectedItem.ItemContainerGenerator.ContainerFromIndex(selectedIndex);
                    }