how to load data in dropdownlist in asp.net?

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 Dropdownlist_click_data_in_textbox { public partial class _Default : System.Web.UI.Page { string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString; string str; SqlCommand com; protected void Page_Load(object sender, EventArgs e) { SqlConnection con = new SqlConnection(strConnString); if (!IsPostBack) { DropDownList1.Items.Add("Choose ItemCode"); con.Open(); str = "select * from employee"; com = new SqlCommand(str, con); SqlDataReader reader = com.ExecuteReader(); while (reader.Read()) { DropDownList1.Items.Add(reader["ItemCode"].ToString()); } reader.Close(); con.Close(); } }