Linq to entities - searching in EntityCollection navigation properties - linq

Question

We have classes
public Invoice: EntityObject
{
public EntityCollection<InvoicePosition> Positions { get {...}; set{...}; }
...
}
public InvoicePosition: EntityObject
{
public string GroupName { get {...}; set{...}; }
}
We are given IQueryable<Invoice>, we are not given IQueryable<InvoicePosition>. How should I find invoices that have positions, where GroupName is 'Fuel'?
IQueryable<Invoice> invoices = InvoiceRepository.List();
IQueryable<Invoice> invoicesThatHaveFuelPositions =
from i in invoices
where ?
select i
EntityFramework should be able to translate it to proper sql query.
EDIT
As Mark Seemann wrote, I can use:
IQueryable<Invoice> invoices = InvoiceRepository.List().Include("Positions").Include("OtherInclude");
IQueryable<Invoice> invoicesThatHaveFuelPositions =
from i in invoices
from p in i.Positions
where p.GroupName = 'Fuel'
select i;
There is a problem. When I use this filtering, I lose "OtherInclude". I think that this is not proper way of filtering when using EF. I'll have to change it to:
IQueryable<Invoice> invoices = InvoiceRepository.List().Include("Positions").Include("OtherInclude");
IQueryable<Invoice> invoicesThatHaveFuelPositions = invoices.Where(???);
But what should I write in Where?
EDIT
Changed Include("Position") to Include("Positions").
EDIT
Alex James gave link to the tip (http://blogs.msdn.com/alexj/archive/2009/06/02/tip-22-how-to-make-include-really-include.aspx), which suggests:
IQueryable<Invoice> invoicesThatHaveFuelPositions =
from i in invoices
where i.Positions.Any(p => p.GroupName == 'Fuel')
select i;
It seems to work and doesn't influence EF includes.

Answer 1

Building on Marks answer. If you do this:
var q = from i in invoices.Include("something")
from p in i.Positions
where p.GroupName == "Fuel"
select i;
The include is lost (see this tip) because the EF loses all includes if the shape of the query changes, for example if you do implicit joins like in a SelectMany query, aka from from.
The workaround is to write your query, and then at the end apply the Include.
Something like this:
var q = ((from i in invoices
from p in i.Positions
where p.GroupName == "Fuel"
select i) as ObjectQuery<Invoice>).Include("something");
If you do this the Entity Framework actually does the include.
Hope this helps
Alex

Answer 2

Something like this ought to work:
var q = from i in invoices
from p in i.Positions
where p.GroupName == "Fuel"
select i;
However, that uses the navigation property Positions, which by default isn't loaded (the Entity Framework uses explicit loading). It will, however, work, if the invoices variable was created like this:
var invoices = from i in myObjectContext.Invoices.Include("Positions")
select i;