TblAreaBLL bll = new TblAreaBLL();

        private void button1_Click(object sender, EventArgs e)

        {

            LoadDataToTree(this.treeView1.Nodes, bll.GetTblAreaListByID());

        }

        private void LoadDataToTree(TreeNodeCollection treeNode, List<TblArea> list)

        {

            foreach (TblArea arr in list)

            {

                TreeNode tree = treeNode.Add(arr.AreaName);

                tree.Tag = arr.AreaId;

                LoadDataToTree(tree.Nodes, bll.GetTblAreaListByID(arr.AreaId)); //递归循环

            }

        }

        private void button2_Click(object sender, EventArgs e)

        {

            List<TblArea> list = bll.GetTblAreaList(); //获取所有的城市升级列表

            LoadDataToTree2(this.treeView1.Nodes, list, ); //先加载所有省级列表

        }

        private void LoadDataToTree2(TreeNodeCollection treeNode, List<TblArea> list, int pid)

        {

            foreach (TblArea arr in list)

            {

                if (arr.AreaPId == pid)

                {

                    TreeNode tree = treeNode.Add(arr.AreaName);

                    tree.Tag = arr.AreaId;

                    LoadDataToTree2(tree.Nodes, list, arr.AreaId); //递归循环  直接在集合中查询。

                }

            }

        }

        //删除节点下的所有数据

        private void button3_Click(object sender, EventArgs e)

        {

            TreeNode node = this.treeView1.SelectedNode;

            if (node != null)

            {

                int areaId = (int)node.Tag;

                bll.DeleteTblAreaDiGui(areaId);

                this.treeView1.SelectedNode.Remove();

                MessageBox.Show("删除成功！");

            }

        }