System.InvalidCastException: 指定的转换无效。

 floor = (int)aRow["FID"].ToString();                //floor = int.Parse(aRow["FID"].ToString());//错误：指定的转换无效

                roomNum = Convert.ToInt32(aRow["RoomId"]) - 100 * floor;                if (roomNum > 14)                    roomNum = roomNum - 2;                status = aRow["SName"].ToString().Trim();