从DB中读取数据到TreeView中

有2张表，结构如下：
表province结构：province_id   province_name   （ primary key:province_id）
表city结构：city_id,city_name,province_id       （primary key:city_id,province_id）

        SqlConnection conn = new SqlConnection("server=zzy;integrated security=sspi;database=test");
        SqlDataAdapter da;
        DataSet ds = new DataSet();
        private void Form1_Load(object sender, EventArgs e)
        {
            readNodes();
            this.treeView1.ExpandAll();
        }
        private void readNodes()
        {
            string _sql = "select * from province";
            da = new SqlDataAdapter(_sql, conn);
            da.Fill(ds, "province");
            DataView dvw1 = new DataView(ds.Tables["province"]);
            int i = 0;
            foreach (DataRowView myRow1 in dvw1)
            {
                string strProvinceName = myRow1["province_name"].ToString().Trim();
                this.treeView1.Nodes.Add(new TreeNode(strProvinceName));//read ParentNode
  //---------------------------------------------------------------------------------------------------------------------------------------//
                da = new SqlDataAdapter("select * from city where province_id='"+myRow1["province_id"].ToString().Trim()+"'",conn);
                da.Fill(ds,"city");
                DataView dvw2 = new DataView(ds.Tables["city"]);
                foreach (DataRowView myRow2 in dvw2)
                {
                    string strCityName = myRow2["city_name"].ToString().Trim();
                    this.treeView1.Nodes[i].Nodes.Add(new TreeNode(strCityName));//read ChildNode
                }
                i++;
                ds.Tables["city"].Clear();
                this.treeView1.SelectedNode = treeView1.Nodes[0];
            }
        }

结果如下：


备注：以上代码所展示的TreeView只支持2层树结构（跟我测试的Table结构有关），方法比较原始，呵呵，若要扩展可以通过递归调用来实现树型结构的结点读取！