Bind multiple values from database dropdownlist

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm4.aspx.cs" Inherits="Dropdownlist" %>

<!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 Dropdownlist
{
    public partial class WebForm4 : System.Web.UI.Page
    {
        string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
        string str;
        SqlCommand com;
        SqlDataAdapter sqlda;
        DataSet ds;

        protected void Page_Load(object sender, EventArgs e)
        {
            SqlConnection con = new SqlConnection(strConnString);
         
            con.Open();
            str = "select * from employee";
            com = new SqlCommand(str, con);
            sqlda = new SqlDataAdapter(com);
            ds = new DataSet();
            sqlda.Fill(ds, "employee");
            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
            {
                DropDownList1.Items.Add(ds.Tables[0].Rows[i]["empname"] +"---" + ds.Tables[0].Rows[i]["empaddress"].ToString());
            }
            con.Close();
        }
    }
}