MySqlCommand参数不起作用

        + "lineName = ?productLine "                       
        + "and isVisible = 1 ";
    MySqlDataAdapter adap = new MySqlDataAdapter(sql, msc);
    adap.SelectCommand.Parameters.Add("?productLine", productLine);

删除撇号(').

将@更改为？,这是MySql查询中参数的前缀.