TreeView连接数据

 string connectionString = "Provider=Microsoft.Jet.OLEDB.4.0;User ID=Admin;Data Source='" + HttpContext.Current.Server.MapPath("~/LHB_DataBase/rss.mdb") + "';Jet OLEDB:Engine Type=5;Jet OLEDB:Database Locking Mode=1;Jet OLEDB:Global Partial Bulk Ops=2;Jet OLEDB:Global Bulk Transactions=1;Jet OLEDB:Create System Database=False;Jet OLEDB:Encrypt Database=False;Jet OLEDB:Don't Copy Locale on Compact=False;Jet OLEDB:Compact Without Replica Repair=False;Jet OLEDB:SFP=False";
        OleDbConnection cn = new OleDbConnection();
        OleDbCommand cmd = new OleDbCommand();

        private void TreeViewOpeartor()
        ...{
            this.TreeView1.Nodes.Clear();
            string OledbString = "select * from categories ";
            DataTable rss_Url = this.GetRss_Url();
            cn.ConnectionString = connectionString;
            cn.Open();
            cmd.Connection = cn;
            cmd.CommandText = OledbString;
            OleDbDataReader dda = cmd.ExecuteReader();
            while(dda.Read())
            ...{
                TreeNode theNode = new TreeNode ();
                theNode.Text = dda["categoryname"].ToString();
                theNode.NodeData = dda["ID"].ToString();
                this.TreeView1.Nodes.Add(theNode);
                DataRow[] urls = rss_Url.Select("categoryID=" + dda["ID"].ToString());
                for(int i = 0 ; i < urls.Length ; i++)
                ...{
                    Microsoft.Web.UI.WebControls.TreeNode node = new Microsoft.Web.UI.WebControls.TreeNode();
                    node.Text = urls[i]["Rss_name"].ToString();
                    node.Target = urls[i]["Id"].ToString();
                    node.NodeData = urls[i]["ID"].ToString();
                    theNode.Nodes.Add(node);
                }
            }
            dda.Close();
            cn.Close();
        }

    
        private DataTable GetRss_Url()
        ...{
            cn.ConnectionString = connectionString ;
            OleDbDataAdapter dda = new OleDbDataAdapter("select * from rss where releasetoweb=1 ",cn);
            DataTable dt = new DataTable();
            dda.Fill(dt);
            return dt;
        }