Question

I have a DataLayer class (LINQ2SQL, not entity framework) that returns rows from the database as follows:

    public ReadOnlyCollection<UserCars> Cars
    {
        get
        {
            using (var context = new TransportopiaDataContext())
            {
                var result = (from car in context.UserCars
                              where car.UserId == UserId
                              select car);
                return result.ToList().AsReadOnly();
            }
        }
    }

Now, as you know, you have to do the ToList() because the datacontext goes out of scope when you leave the using() clause. The problem is that there are foreign key relationships; while the context is still in scope, you could do:

string foo = car.Manufacturer.Name;

But doing that after context has been disposed causes an error. So my question is:

“Is there some way of doing the ToList() such that foreign key relationships will also be expanded?”

Answer 1

You can specify this in the DataLoadOptions before executing your query:

using (var context = new TransportopiaDataContext())
{
    DataLoadOptions options = new DataLoadOptions();
    options.LoadWith<UserCar>(x => x.Manufacturer);
    context.LoadOptions = options;
    var result = (from car in context.UserCars
                    where car.UserId == UserId
                    select car);
    return result.ToList().AsReadOnly();
}