dropdownlist bind

 SqlConnection con = new SqlConnection("Data Source=ANKITA-USER18\\SQL2008R2;Integrated Security=True;Initial Catalog=hrdemo");
        con.Open();
        SqlCommand cmd = new SqlCommand("select * from emp", con);
        SqlDataReader dr = cmd.ExecuteReader();
        while (dr.Read())
        {
            String str = dr[0].ToString() + "  :" + dr[1].ToString();
            DropDownList1.Items.Add(str);
        }