c# - 从对象类型WebMatrix.Data.DynamicRecord到已知托管提供程序 native 类型的映射不存在

Question

我对我的SQL Server返回的错误感到非常困惑-这是什么引起的？

我正在运行的C#代码是:

List<CalendarEvent> events = new List<CalendarEvent>();
        var db = Database.Open("myDatabase");
        string username = HttpContext.Current.Request.Cookies.Get("username").Value;
        var listOfGroups = db.Query("SELECT GroupID FROM Membership WHERE UserID = (SELECT UserID from Users WHERE Username = @0 )",  username);

        foreach(var groupID in listOfGroups)
            {
                var result = db.Query(
                    @"SELECT e.event_id, e.title, e.description, e.event_start, e.event_end, e.group_id, e.recurring
                    FROM   event e
                    JOIN   Membership m ON m.GroupID = e.group_id
                    WHERE  e.recurring = 0
                    AND    m.GroupID = @0
                    AND    e.event_start >= @1
                    AND    e.event_end <= @2
                    UNION ALL
                    SELECT e.event_id, e.title, e.description, DATEADD(week, w.weeks, e.event_start), DATEADD(week, w.weeks, e.event_end), e.group_id, e.recurring
                    FROM   event e
                JOIN   Membership m ON m.GroupID = e.group_id
                CROSS JOIN 
                    ( SELECT  row_number() OVER (ORDER BY Object_ID) AS weeks
                    FROM SYS.OBJECTS
                    ) AS w
                    WHERE  e.recurring = 1
                    AND    m.GroupID = $3
                    AND    e.event_start >= @4
                    AND    e.event_end <= @5", groupID, start, end, groupID, start, end
                );
                foreach(var record in result)
                    {
                            CalendarEvent cevent = new CalendarEvent();
                            cevent.id = record.event_id;
                            cevent.title = record.title;
                            cevent.description = record.description;
                            cevent.start = record.event_start;
                            cevent.end = record.event_end;
                            cevent.recurring = record.recurring;
                            events.Add(cevent);
                    }
            }
        return events;
}

错误:

Exception Details: System.ArgumentException: No mapping exists from object type WebMatrix.Data.DynamicRecord to a known managed provider native type.

是什么原因造成的，我该如何解决？

我想做的是返回我希望在其一周以及此后52周返回的所有重复发生= 0的事件，以及所有重复发生= = 1的事件。

Answer 1

看来您的问题出在groupID输入参数上。

var listOfGroups = db.Query("SELECT GroupID FROM Membership WHERE UserID = (SELECT UserID from Users WHERE Username = @0 )",  username);

您的 listOfGroups将作为 WebMatrix.Data.DynamicRecord对象的集合返回。您似乎只需要 int值，因为您在 groupID语句中获得了 foreach(var groupID in listOfGroups)。

尝试代替最后一行:

AND    e.event_end <= @5", groupID, start, end, groupID, start, end

与:

AND    e.event_end <= @5", (int)groupID.GroupID, start, end, (int)groupID.GroupID, start, end

这应该从每个动态查询结果的第一列(也是唯一列)中提取值，该值就是您要获取的int组ID。

编辑: DynamicRecord查询结果的更正值调用语法。