为什么读取不了父结点下的子结点???

Question

表province结构：province_id,province_name
表city结构：city_id,city_name,province_idSqlConnection conn = new SqlConnection("server=zzy;integrated security=sspi;database=test");
        SqlDataAdapter da;
        DataSet ds = new DataSet();
        string strProvinceName = "", strProvinceId = "", strCityName = "";
        private void Form1_Load(object sender, EventArgs e)
        {
            define_dataGridView();
            string _sql = "select * from province";
            da = new SqlDataAdapter(_sql, conn);
            da.Fill(ds, "province");
            for (int i = 0; i < ds.Tables["province"].Rows.Count; i++)
            {
                strProvinceName = ds.Tables["province"].Rows[i][1].ToString();
                strProvinceId = ds.Tables["province"].Rows[i][0].ToString();
                this.treeView1.Nodes.Add(new TreeNode(strProvinceName)); //read the parentroot
                TreeNode parentRoot = new TreeNode(strProvinceName);
                string _strsql = "select * from city where province_id='" + strProvinceId + "'";
                ds.Tables.Add("city");
                da = new SqlDataAdapter(_strsql, conn);
                ds.Tables["city"].Clear();
                da.Fill(ds.Tables["city"]);
                for (int j = 0; j < ds.Tables["city"].Rows.Count; j++)
                {
                    strCityName = ds.Tables["city"].Rows[j][1].ToString();
                    parentRoot.Nodes.Add(new TreeNode(strCityName)); //read the childroot
                }
            }
        } 大家帮忙看看，非常感谢！

Answer 1

for (int i = 0; i < ds.Tables["province"].Rows.Count; i++)
            {
                strProvinceName = ds.Tables["province"].Rows[i][1].ToString();
                strProvinceId = ds.Tables["province"].Rows[i][0].ToString();
                TreeNode parentRoot = new TreeNode(strProvinceName);
                string _strsql = "select * from city where province_id='" + strProvinceId + "'";
                da.SelectCommand.CommandText = _strsql;
                da.Fill(ds.Tables["city"]);
                for (int j = 0; j < ds.Tables["city"].Rows.Count; j++)
                {
                    strCityName = ds.Tables["city"].Rows[j][1].ToString();
                    parentRoot.Nodes.Add(new TreeNode(strCityName)); //read the childroot
                }
                this.treeView1.Nodes.Add(parentRoot);
            }

Answer 2

另外 你这种：strCityName = ds.Tables["city"].Rows[j][1].ToString();
最好写成 strCityName = ds.Tables["city"].Rows[j][“字段名”].ToString();比较易读

Answer 3

hoho~~
         
       da.Fill(ds.Tables["city"]);
改成 
       da.Fill(ds,"city");写太快 没注意 

Answer 4

为什么不一次把所有的市都读出来
然后用datatable.Select方法筛选数据？？每个省底下的市都要读数据库？？？？

Answer 5

this.treeView1.Nodes.Add(new TreeNode(strProvinceName)); //read the parentroot
TreeNode parentRoot = new TreeNode(strProvinceName);
--〉
这得问题
你new 了两次

Answer 6

我换了个写法，成功了。不过还需要改进，因为我写的这个只支持2层树结构，呵呵！
      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];
            }
        }

Answer 7

谢谢winner8080，代码已经收到，谢谢你的帮助，非常感谢！