Question

I am using

var s = db.sModels.ToList().First(r => r.Status == CustomStatus.Available);

to fetch the first available item.

However, when fetched, a foreign key in s turns out to be null.

I have connected to the database and saw that the foreign key is not null (but is 1).

Why does it become null?

Answer 1

Assuming this is Linq to Entities – that is the default behavior – if you want to materialize the related entity – let’s say SomeEntity you can use an Include query in which case the FK and entity will be populated:

var s = db.sModels.Include(r=> r.SomeEntity)
                  .First(r => r.Status == CustomStatus.Available);

For a workaround w/o using an Include query to just retrieve the FKs see this blog post: “Getting Foreign Key Values with Linq-to-Entities”

As noted in a comment to the question Linq to Entities does not support enums right now hence above would actually not work as is. As a workaround (until EF 5) you can use integers on the DB for now:

int statusAvailable = (int) CustomStatus.Available;
var s = db.sModels.Include(r=> r.SomeEntity)
                  .First(r => r.Status == statusAvailable);