How do I show the value in dropdown list from database?

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.Web.Configuration;
using System.Configuration;

namespace LifeTime
{
    public partial class index : System.Web.UI.Page
    {
        //static Configuration rootWebConfig = WebConfigurationManager.OpenWebConfiguration("/LifeTime");
        //SqlConnection con = null;
        //string constr = ConfigurationManager.ConnectionStrings["LifetimeConnection"].ConnectionString;
        //System.Configuration.Configuration webconfig = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(null);
        //const string CONSTRINGNAME = "LifetimeConnection";
        //ConnectionStringSettings conString = rootWebConfig.ConnectionStrings.ConnectionStrings[CONSTRINGNAME];
        //SqlConnection con = new SqlConnection(rootWebConfig.ConnectionStrings[CONSTRINGNAME].ConnectionStrings);
        protected void Page_Load(object sender, EventArgs e)
        {
            //SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["LifetimeConnection"].ConnectionString);
            //SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog = Sample;Trusted_Connection=true;");
            //Response.Write(con);
            //SqlCommand cmd = new SqlCommand("Select ID,location_name from dbo.location where flag = 0;",con);
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["LifetimeConnection"].ConnectionString);

            try
            {
                Response.Write("Hi Hello");
                con.Open();
                Response.Write("Con is opened");
                SqlCommand cmd = new SqlCommand("Select top 1 * from location;", con);
                dropdownlist.DataSource = cmd.ExecuteReader();
                dropdownlist.DataBind();
                dropdownlist.DataTextField = "location_name";
                dropdownlist.DataValueField = "ID";
                dropdownlist.DataBind();
            }
            catch (Exception ex)
            {

            }
            finally
            {
                con.Close();
            }
        }
    }
}