从数据库中读取数据到TreeView中

                                            

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
public partial class _Default : System.Web.UI.Page
{
    SqlConnection conn = new SqlConnection("server=zhan;uid=sa;pwd=zhan;database=test");
    SqlDataAdapter da;
    DataSet ds = new DataSet();

    protected void Page_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
                    treeView1.Nodes[i].ChildNodes.Add(new TreeNode(strCityName));
                }
                i++;
                ds.Tables["city"].Clear();
                //treeView1.SelectedNode = treeView1.Nodes[0];
                //treeView1.SelectedNode =treeView1 .Nodes;
            }

    }
}

数据库:
表province：province_id   province_name   (主键:province_id)

表city：city_id,city_name,province_id       (主键:city_id,province_id)