Create XML Dinamically and bind the data in dropdown list and grid view

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Text;
using System.Xml;
using System.IO;

public partial class test : System.Web.UI.Page
{
    string testy="5555";
    string testy1 = "statename";
    protected void Page_Load(object sender, EventArgs e)
    {
        BindXML(testy, testy1);
    }

    private void BindXML(string a, string b)
    {
        string str = "<StateXML>";
        str = str + "<State><State_id>" + a + "</State_id><State_name>" + b + "</State_name></State>";
        str = str + "</StateXML>";
        DataSet ds = new DataSet();
        ds.ReadXml(new StringReader(str));
        ds.WriteXml(Server.MapPath("~/xml_files/Data.xml"));

        string a1 = Convert.ToString(ds.Tables["tablename"].Rows[0]["State_id"]);
        string b1=  Convert.ToString(ds.Tables["tablename"].Rows[0]["State_name"]);

       ddl_rrr.DataSource=ds.Tables["tablename"];
       ddl_rrr.DataTextField = "State_name";
       ddl_rrr.DataValueField = "State_id";

       ddl_rrr.DataBind();

        GridView1.DataSource=ds.Tables["tablename"];
        GridView1.DataBind();



    }
}