winform TreeView树节点上下移动

         /// <summary>
        /// 上移
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void tsbMoveUp_Click(object sender, EventArgs e)
        {
            if (Tv_tree.SelectedNode == null)
            {
                MessageBox.Show("请选择需要移动的的节点！");
                this.Focus();
                return;
            }
            folder  model = new folder();
            TreeNode node = Tv_tree.SelectedNode;     //获得选中节点的值
            model.folderId = node.Tag.ToString();
            model.TheOrder = node.Name.ToString();
            if (node.PrevNode == null)      //选中节点的上一个节点为Null则返回
            {
                return;
            }
            folder upModel = new folder();
            TreeNode upNode = node.PrevNode;            //获得选中节点的上一个节点
            upModel.folderId = upNode.Tag.ToString();
            upModel.TheOrder = upNode.Name;
            bool flag = folderOperation.MoveUp(model, upModel);       //将两个节点的排序编号互换
            if (flag)       //如果执行成功
            {
                string theOrder = node.Name;
                node.Name = upNode.Name;
                upNode.Name = theOrder;
                TreeNode newNode = (TreeNode)node.Clone();      //克隆选中的节点
                if (node.Parent == null)
                {
                    Tv_tree.Nodes.Insert(upNode.Index, newNode);      //在选中节点的上一个节点的地方插入本节点
                }
                else
                {
                    node.Parent.Nodes.Insert(upNode.Index, newNode);
                }
                node.Remove();
                Tv_tree.SelectedNode = newNode;
            }
            else
            {
                return;
            }
        }
        /// <summary>
        /// 下移
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void tsbMoveDown_Click(object sender, EventArgs e)
        {
            if (Tv_tree.SelectedNode == null)
            {
               MessageBox.Show("请选择需要移动的的节点！");
                this.Focus();
                return;
            }
            folder model = new folder();
            TreeNode node = Tv_tree.SelectedNode;     //选中的节点
            model.folderId = node.Tag.ToString();
            model.TheOrder = node.Name.ToString();
            if (node.NextNode == null)      //下一个节点为Null时返回
            {
                return;
            }
            folder downModel = new folder();
            TreeNode dowNode = node.NextNode;
            downModel.folderId = dowNode.Tag.ToString();
            downModel.TheOrder = dowNode.Name;
            bool flag = folderOperation.MoveUp(model, downModel);
            if (flag)
            {
                string theOrder = node.Name;
                node.Name = dowNode.Name;
                dowNode.Name = theOrder;
                TreeNode newNode = (TreeNode)dowNode.Clone();       //克隆下一个节点及其所有的子节点
                if (node.Parent == null)
                {
                    Tv_tree.Nodes.Insert(node.Index, newNode);    //在原节点的位置插入下一个节点的值
                }
                else
                {
                    node.Parent.Nodes.Insert(node.Index, newNode);
                }
                dowNode.Remove();           //删除掉选中节点的下一个节点
                Tv_tree.SelectedNode = node;  //重新选中
            }
            else
            {
                return;
            }
        }

 string sql = string.Format("update folder set theorder = '{0}' where folderid = '{1}'", model.TheOrder, upModel.folderId);
 string sql1 = string.Format("update folder set theorder = '{0}' where folderid = '{1}'", upModel.TheOrder, model.folderId);