No mapping exists from object type WebMatrix.Data.DynamicRecord to a known managed provider native type

Question

I am very confused with the error my SQL server is returning - what would be
causing this?

The C# code I am running is :

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;
}

And the error:

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

What could be causing this and how can I fix it ?

What I wish to do is return all events where recurring = 0, and any events
where recurring =1 I want to be returned for their week and the 52 weeks
thereafter.

Answer 1

Looks like your issue is with your groupID input parameter.

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

Your listOfGroups is coming back as a collection of the
WebMatrix.Data.DynamicRecord objects. You seem to want just the int value,
as you get groupID in the foreach(var groupID in listOfGroups) statement.

Try instead replacing the last line:

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

with:

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

This should pull the value from the first (and only) column of each dynamic
query result, that value being the int group ID that you are after.

EDIT: Corrected value call syntax of DynamicRecord query result.