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);