Entity Framework Code First 4.3 / LINQKit predicate for related table

Question

I am using Entity Framework 4.3.1 with a Code First approach. Also, I am using LinqKit so as to use the PredicateBuilder.

If I have tables like so:

Location,

Answer 1

After about a week's worth of struggling, I found out that you can in fact do this. The steps are:

1. Define a Predicate that is the query for your inner property (subPredicate)
2. Invoke that subPredicate from within another Predicate (predicate), against the property of the parent object.
3. Expand your predicate when using it in your Where clause.

Here's the revised code for your example:

var subPredicate = PredicateBuilder.True();
subPredicate = subPredicate.And(tz => tz.TimeZoneCode == "EST");

var predicate = PredicateBuilder.True();
predicate = predicate.And(l => subPredicate.Invoke(l.TimeZone));

List locations = context.Locations
    .AsExpandable().Where(pred.Expand())
    .Select(loc => loc).ToList();