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！