绑定下拉列表的最佳方法是什么

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;


namespace WebApplication1
{
    public partial class Details : System.Web.UI.Page
    {
        SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ABCConnectionString2"].ConnectionString);
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                SqlCommand cmd = new SqlCommand();
                cmd.CommandText = "Select * from emp_details";
                cmd.Connection = conn;
                conn.Open();
               // SqlDataAdapter ds = new SqlDataAdapter("Select * from emp_details ",conn);
                DataTable dt = new DataTable();

                dt.Load(cmd.ExecuteReader());
                conn.Close();
                //DataTable dt = new DataTable();
                //ds.Fill(dt);
                DropDownList1.DataSource = dt;
              // DropDownList1.DataSource = dt.Tables[0];

                DropDownList1.DataTextField = "emp_name";
                DropDownList1.DataValueField = "emp_Id";
                DropDownList1.DataBind();
                //conn.Close();
            }
        }

        protected void Button_submit_Click(object sender, EventArgs e)
        {

            SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["ABCConnectionString2"].ConnectionString);
            conn.Open();
            string InsertQuery = "insert into emp_details set(emp_name,father_name,age,sex,dob,nationality,state,city,mobile_no,exp,qual,emp_sal,email) values(@name,@fname,@age,@sex,@dob,@nation,@state,@city,@mob,@exp,@qual,@sal,@email) ";
            SqlCommand com = new SqlCommand(InsertQuery, conn);
            
            com.Parameters.AddWithValue("@name", TextBox_emp_name.Text);
            com.Parameters.AddWithValue("fname", TextBox_father_name.Text);
            com.Parameters.AddWithValue("@age", TextBox_Age.Text);
            com.Parameters.AddWithValue("@sex", RadioButtonList_sex.Text);
             com.Parameters.AddWithValue("@dob", TextBox_dob.Text);
            com.Parameters.AddWithValue("@nation", TextBox_nationality.Text);
            com.Parameters.AddWithValue("@state", TextBox_state.Text);
            com.Parameters.AddWithValue("@city", TextBox_city.Text);
             com.Parameters.AddWithValue("@mob", TextBox_mob.Text);
             com.Parameters.AddWithValue("@exp", DropDownList_exp.Text);
             com.Parameters.AddWithValue("@qual", DropDownList_qual.Text);
             com.Parameters.AddWithValue("@sal", TextBox_sal.Text);
             com.Parameters.AddWithValue("@email", TextBox_email.Text);
            com.ExecuteNonQuery();
            conn.Close();
            Response.Write("Insertion Succesfull");
        }

        protected void Button_update_Click(object sender, EventArgs e)
        {
            conn.Open();
            string updateQuery = "update emp_details(emp_name,father_name,age,sex,dob,nationality,state,city,mobile_no,exp,qual,emp_sal,email) values(@name,@fname,@age,@sex,@dob,@nation,@state,@city,@mob,@exp,@qual,@sal,@email) ";
            SqlCommand com = new SqlCommand(updateQuery, conn);

            com.Parameters.AddWithValue("@name", TextBox_emp_name.Text);
            com.Parameters.AddWithValue("fname", TextBox_father_name.Text);
            com.Parameters.AddWithValue("@age", TextBox_Age.Text);
            com.Parameters.AddWithValue("@sex", RadioButtonList_sex.Text);
            com.Parameters.AddWithValue("@dob", TextBox_dob.Text);
            com.Parameters.AddWithValue("@nation", TextBox_nationality.Text);
            com.Parameters.AddWithValue("@state", TextBox_state.Text);
            com.Parameters.AddWithValue("@city", TextBox_city.Text);
            com.Parameters.AddWithValue("@mob", TextBox_mob.Text);
            com.Parameters.AddWithValue("@exp", DropDownList_exp.Text);
            com.Parameters.AddWithValue("@qual", DropDownList_qual.Text);
            com.Parameters.AddWithValue("@sal", TextBox_sal.Text);
            com.Parameters.AddWithValue("@email", TextBox_email.Text);
            com.ExecuteNonQuery();
            conn.Close();
            Response.Write("Updation Succesfull");
        }

        protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
        {
            SqlDataAdapter ds = new SqlDataAdapter("Select *  from emp_deatils where emp_name='"+DropDownList1.Text+"' ", conn);
            DataTable dt = new DataTable();
            ds.Fill(dt);
            TextBox_father_name.Text = dt.Rows[0][1].ToString();
            TextBox_Age.Text = dt.Rows[0][2].ToString();
            RadioButtonList_sex.Text = dt.Rows[0][3].ToString();
            TextBox_dob.Text = dt.Rows[0][4].ToString();
            TextBox_nationality.Text = dt.Rows[0][5].ToString();
            TextBox_state.Text = dt.Rows[0][6].ToString();
            TextBox_city.Text = dt.Rows[0][7].ToString();
            TextBox_mob.Text = dt.Rows[0][8].ToString();
            DropDownList_exp.Text = dt.Rows[0][9].ToString();
            DropDownList_qual.Text = dt.Rows[0][10].ToString();
            TextBox_sal.Text = dt.Rows[0][11].ToString();
            TextBox_email.Text = dt.Rows[0][12].ToString();

            DropDownList1.DataBind();


        }

        protected void Button_delete_Click(object sender, EventArgs e)
        {

        }