Fix zeroth index as Select in dropdownlist

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="Fix_zeroth_index_in_dropdownlist._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:DropDownList ID="DropDownList1" runat="server">
        </asp:DropDownList>
    </div>
    </form>
</body>
</html>


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 Fix_zeroth_index_in_dropdownlist
{
    public partial class _Default : System.Web.UI.Page
    {
        string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        string str;
        DataSet ds;
        SqlCommand com;
        SqlDataAdapter sqlda;

        protected void Page_Load(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(strConnString);
            con.Open();
            str = "select * from  employee";
            com = new SqlCommand(str, con);
            ds = new DataSet();
            sqlda = new SqlDataAdapter(com);
            sqlda.Fill(ds,"employee");
            if(ds.Tables[0].Rows.Count>0)
            {
             DropDownList1.Items.Clear();
             DropDownList1.Items.Add(new ListItem("--Select--", "0"));
             foreach (DataRow dr in ds.Tables[0].Rows)
             {
                 DropDownList1.Items.Add(new ListItem(dr["empname"].ToString()));
             }
            }
        }
    }
}