How To Bind Data Retrived From Sql Db To DropDownLists?

 Hello all,
I just have problems to bind the data to dropdownlists, and my code is written as:  SqlConnection myConnection;

            SqlCommand myCommand;
            SqlDataReader myReader;

            myConnection = new SqlConnection();
            myConnection.ConnectionString = ConfigurationManager.ConnectionStrings["NorthWindConnectionString"].ConnectionString;

            myCommand = new SqlCommand();
            myCommand.CommandText = "select PostalCode from Customers order by PostalCode asc";
            myCommand.CommandType = CommandType.Text;
            myCommand.Connection = myConnection;

            myCommand.Connection.Open();
            myReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection);
            DropDownList1.DataSource = myReader;
            DropDownList1.DataBind();

            myCommand.Dispose();
            myConnection.Dispose();
Any idea? Thanks