Do some of Castle ActiveRecord's LINQ operators not work?

I'm working with an object model in Castle ActiveRecord that represents pregnant women. It's a simple tree structure:

Patient
  Visit
    Delivery

A Patient has 0 or more Visits and a Visit has 0 or more Deliveries. I've mapped everything to the database, and I can loop through the Patient>Visit>Delivery hierarchy and print out everything. I can also use LINQ Where clauses like this:

var recent = new DateTime(1980, 1, 1);
var patients = ActiveRecordLinq
    .AsQueryable<Patient>()
    .Where(p => p.DateOfBirth > recent)
    .OrderBy(p => p.LastName)
    .ThenBy(p => p.FirstName)
    .ThenBy(p => p.DateOfBirth);

This correctly gives me a list of patients born since 1/1/1980.

Now suppose I want to only look at all the visits for those patients, to analyze them or whatever. I'd think the correct way is something like this:

var visits = patients.SelectMany(p => p.Visits);

Based on how LINQ works, this should give me a flattened list of all the visits of all the patients from the original query. The visits variable does in fact come out as an IQueryable<Visit>. But when I try to enumerate the results, I get this:

Unable to cast object of type 'Patient' to type 'Visit'.

Similarly, I can get the birthdates of several patients like this:

var patients = ActiveRecordLinq.AsQueryable<Patient>().Take(10);
var birthDates = patients.Select(x => x.DateOfBirth);
foreach (var date in birthDates.ToList().OrderBy(x => x))
{
    Debug.Print(date.ToShortDateString());
}

But if I take out that ToList in the foreach, I get a NullReferenceException.

Clearly there are some things about the Castle ActiveRecord implementation of LINQ (or its NHibernate base) that I'm failing to grasp. Can anyone offer me some help?

ansaurus

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Do some of Castle ActiveRecord's LINQ operators not work?

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