下拉列表无级数据绑定

private string toadd = "├".

private void GetArticleCategory(string pid)

     {

         SqlConnection conn = new SqlConnection("server=.;database=test;uid=sa;pwd=;");

         string sql = "select Articlesgroup_id,Groupname from Articlesgroup where Articlesgroup_parent_id=@pid order by Groupname";

         SqlCommand cmd = new SqlCommand(sql, conn);

         SqlParameter Pid = new SqlParameter("@pid", SqlDbType.Int);

         Pid.Value = pid;

         cmd.Parameters.Add(Pid);

         conn.Open();

         SqlDataReader sdr = cmd.ExecuteReader();

         while (sdr.Read())

         {

             this.DropDownList1.Items.Add(new ListItem(toadd + " " + sdr[1].ToString(), sdr[0].ToString()));

             toadd += "─┴";

             this.GetArticleCategory(sdr[0].ToString());

           toadd = toadd.Substring(0, toadd.Length - 2);  

         }

         sdr.Close();

         conn.Close();

     }

   protected void Page_Load(object sender, EventArgs e)

     {

         this.keyword.Attributes.Add("onfocus","if( this.value=='key key key') {this.value='' };");

         if (!Page.IsPostBack)

         {

             this.GetArticleCategory("0");

         }

         this.DropDownList1.Items.Insert(0, new ListItem("Search All", "all"));

     }