Question

I am battling to work out how to handle foriegn keys with Entity Framework, when editing or adding a new record. For example, I have a person table, which has a timezone_id linking to my timezone table.

But the model seems to not include timezone_id. I see it’s a new way of doing things, but … how do I store my record?

My method:

 public static string CreateUser(string username, string email, string password, string firstname, string surname, int timezoneId)
    {
        user u = new user();
        u.surname = surname;
        u.firstname = firstname;
        u.email = email;
        u.password = password;
        u.username = username;
        Db.AddTousers(u);

        Db.SaveChanges();

        return username;

    }

I can’t do u.timezone_id = timezoneid;

I only have u.timezone (which seems to be the actual entity), and u.timezoneReference, which I am not sure what to do with.

Answer 1

I think you have to fill in the timezone entity from the database, i.e.

u.timezone = DB.TimezoneSet.FirstOrDefault(tz => tz.Id == timezoneid);

assuming you’ve generated the set name with EF3; it’ll be DB.Timezones by default in EF4. If this is EF4 then you can also regenerate your EDMX for that table with ID columns included too – there’s an option on the front page of the wizard.

The TimezoneReference property is used to test whether child entities have been loaded, force them to load, etc.