Question

我正在尝试用C＃写一个SQL查询到Access。该查询在Access软件中工作正常，但是当我尝试通过带参数的C＃运行它时，它会抛出参数丢失的异常。它就像它忽略了我给出的参数。这是我的方法：

public DataTable GetRoomStatusByDate(Room RoomItem, TimeRange TimeItem, WeekDay DayItem, DateTime DateItem)
        {
            string cmdStr = "SELECT Subject, AdditionOrCancellation, Description " + 
                            "FROM (SELECT * " + 
                                "FROM TimeTables TT1 LEFT OUTER JOIN SpecialEvents SE1 " + 
                                "ON TT1.RoomNumber = SE1.RoomNumber AND TT1.StructureNumber = SE1.StructureNumber AND " +
                                "TT1.DayNumber = SE1.DayNumber AND TT1.HourNumber = SE1.HourNumber " + 
                                "UNION " + 
                                "SELECT * " + 
                                "FROM TimeTables TT2 RIGHT OUTER JOIN SpecialEvents SE2 " + 
                                "ON TT2.RoomNumber = SE2.RoomNumber AND TT2.StructureNumber = SE2.StructureNumber " + 
                                "AND TT2.DayNumber = SE2.DayNumber AND TT2.HourNumber = SE2.HourNumber) " +
                            "WHERE (TT1.RoomNumber = @TTRoomNumber OR SE1.RoomNumber = @SERoomNumber) AND (TT1.StructureNumber = @TTStructureNumber OR SE1.StructureNumber = @SEStructureNumber) " +
                            "AND(TT1.HourNumber = @TTHourNumber OR SE1.HourNumber = @SEHourNumber) AND (TT1.DayNumber = @TTDayNumber OR SE1.DayNumber = @@SEDayNumber) " +
                            "AND (SE1.EventDate = @SEEventDate OR SE1.EventDate IS NULL)";
            DataSet ds = new DataSet();
            using (OleDbCommand command = new OleDbCommand(cmdStr))
            {
                command.Parameters.AddWithValue("@TTRoomNumber", RoomItem.Number);
                command.Parameters.AddWithValue("@SERoomNumber", RoomItem.Number);
                command.Parameters.AddWithValue("@TTStructureNumber", RoomItem.Structure);
                command.Parameters.AddWithValue("@SEStructureNumber", RoomItem.Structure);
                command.Parameters.AddWithValue("@TTDayNumber", TimeItem.Number);
                command.Parameters.AddWithValue("@SEDayNumber", TimeItem.Number);
                command.Parameters.AddWithValue("@TTDayNumber", DayItem.Number);
                command.Parameters.AddWithValue("@SEDayNumber", DayItem.Number);
                command.Parameters.AddWithValue("@SEEventDate", DateItem);
                ds = GetMultipleQuery(command);
            }
            DataTable dt = new DataTable();
            try
            {
                dt = ds.Tables[0];
            }
            catch
            { }
            return dt;
        }

我还想提一下我使用OLEDB并且我的连接非常好，因为我有很多查询和参数的方法，它们一切正常，没有任何问题。这是我唯一一个查询不起作用的方法。

Answer 1

OleDb使用位置参数，而不是命名参数。在SQL中用?替换参数名称。您可以在AddWithValue中保持参数名称不变，因为它会被忽略。

...
"WHERE (TT1.RoomNumber = ? OR SE1.RoomNumber = ?) AND (TT1.StructureNumber = ? OR SE1.StructureNumber = ?) " +
"AND(TT1.HourNumber = ? OR SE1.HourNumber = ?) AND (TT1.DayNumber = ? OR SE1.DayNumber = ?) " +
"AND (SE1.EventDate = ? OR SE1.EventDate IS NULL)";

确保以与SQL文本中出现的顺序相同的顺序添加参数。

传递给AddWithValue的值也必须具有正确的类型。数字或日期字符串不会自动转换为相应的数字或日期时间类型。

C＃Access无法识别查询中的参数

1 个答案: