Question

Suppose we have 2 types, mapped to a Database via EF 4.

Schedule 1.....1 Visit

Also, we have third custom view type

public class ScheduleView
{
    public Schedule Schedule { get; set; }
    public Visit Visit { get; set; }
}

So we can write the join query

var query = Context.Schedule.Join(Context.Visit
,/*Schedule join key definition*/,/*Visit join key definition*/,
(scheduleView, visit) => new ScheduleView {Schedule = scheduleView, Visit = visit})

The problem is that I need to load also Patient property of Visit type. But when I write

query = (query as ObjectQuery<ScheduleView>).Include("Visit.Patient");

I receive a runtime error

Unable to cast the type
‘System.Linq.IQueryable1' to type
'System.Data.Objects.ObjectQuery1′.
LINQ to Entities only supports casting
Entity Data Model primitive types.

So, the question is – how to force query to include something within my custom type?

Answer 1

Finally, developed some ugly workaround – introduced new member in custom type and explicitly queried for it.

public class ScheduleView
{
    public Schedule Schedule { get; set; }
    public Visit Visit { get; set; }
    **public Patient Patient{ get; set; }**
}

    var query = Context.Schedule.Join(Context.Visit
    ,/*Schedule join key definition*/,/*Visit join key definition*/,
    (scheduleView, visit) => new ScheduleView 
{Schedule = scheduleView, Visit = visit, **Patient = visit.Patient**})

Now I have Patient loading properly in my custom type. Amusing, but when I investigate ScheduleView.Visiting.Patient after introducing ScheduleView.Patient I found it also loaded.
Cant get the EF logic in this case. And dunno how to force loading ScheduleView.Visiting.Patient without having to load useless ScheduleView.Patient 🙁