Return single row in an EF-generated class with its children set ordered in LinqToSql (c#)

I would like to make a simple operation with LinqToSql but I cannot find the right way. I have the following tables, hereby represented with an EF-generated class diagram:

Where the foreign key relationship is on SessionId (primary key table WebinarSession).

I want to make a query that returns 1 WebinarSession with its corresponding children on WebinarTopic, ORDERED by TopicStartTime.

Taking into account that _webinarRecordingsDB is the repository object, I already tried the solutions that looked more logic to me:

WebinarSession lsession = _webinarRecordingsDB.WebinarTopics
    .OrderBy(m => m.TopicStartTime)
    .Select(m => m.WebinarSession)
    .Single(m => m.SessionId == sessionId);

WebinarSession lsession = _webinarRecordingsDB.WebinarSessions
    .Single(m => m.SessionId == sessionId).WebinarTopics
    .OrderBy(m => m.TopicStartTime)
    .Single(m => m.WebinarSession.SessionId == sessionId);

Those launch an exception because they find more rows in WebinarSession. As last (illogical) resort I also tried:

WebinarSession lsession = _webinarRecordingsDB.WebinarSessions
    .Single(m => m.SessionId == sessionId);

lsession.WebinarTopics.OrderBy(m => m.TopicStartTime);

that does not launch any ex开发者_如何学Cception but does not perfor the sorting on lsession. Anybody might help me please? Thanks

EDIT

I want to keep the result in a WebinarSession object

The OrderBy extension method does not does change the collection, but returns a new (ordered) collection. You need to store the results in a variable and use that:

var session = _webinarRecordingsDB.WebinarSessions
    .Single(m => m.SessionId == sessionId);

var topics = session.WebinarTopics.OrderBy(m => m.TopicStartTime);

The Second Option is close, but you have to assign the sorted WebinarTopics back to a new IList or something, such as the following...

WebinarSession lsession = _webinarRecordingsDB.WebinarSessions.Single(m => m.SessionId == sessionId);
List<WebinarTopic> ltopics = lsession.WebinarTopics.OrderBy(m => m.TopicStartTime).ToList();

HTH. Dave