Wpf TreeView根据SelectedItem找选中的TreeViewItem

1. SelectedItem是绑定的DataContext 对象

2. Items是绑定对象集合

两层节点的查找方法，可递归扩展多层

                // 从第一root节点查找
                TreeViewItem selectedItem = _TreeView.ItemContainerGenerator.ContainerFromItem(usercombotable.SelectedItem) as TreeViewItem;
                if (selectedItem != null)
                {
                    return selectedItem;
                }
                else
                {
                    // 遍历root节点
                    foreach (var pItem in usercombotable.Items)
                    {
                        // 获取root节点容器TreeViewItem
                        var rootItem = _TreeView.ItemContainerGenerator.ContainerFromItem(pItem) as TreeViewItem;
                        if (rootItem != null)
                        {
                            // 从子节点查找
                            var selectSubItem = rootItem.ItemContainerGenerator.ContainerFromItem(usercombotable.SelectedItem) as TreeViewItem;
                            if (selectSubItem != null)
                            {
                                return selectSubItem;
                            }
                        }
                    }
                }