How do I prevent EF from reinserting objects of other dbcontext?

Question

I am using EF 4.1 in a MVC 3 project and I am having problems with inserting an object. I am using session as well to hold onto some objects. In concrete :

I have a simple class with a parent child relationship:

public class Event
{
    public User Promotor {get;set;}
}

The promotor is based on the CurrentUser. In my application I store the CurrentUser in http session. Now when I add an event like this the user (and all related objects) gets inserted one more time with a new primary key.

        //1st request inserts/loads the user
        User user;
        using (var context = new MyDbContext())
        {
            user = new User();
            context.Users.Add(user);
            context.SaveChanges();
        }

        //2nd request saves the event 
        var before = db.Users.Count();
        var @event = new Event
        {
            Promotor = user, //user was kept in Session
        };
        db.Entry(@event).State = EntityState.Added;
        db.SaveChanges();

When i check the state of the user it is 'added' as well although the primary key is not 0 and EF should know it is already persistent. How can fix this without adding a lot of to my persistency code. Do I have to reattach my currentuser to the new dbcontext on every request? This will lead to db code 'leaking' into my application. I want to keep the DB stuff in a data layer. I am using a repository like this :

    public void Save(T entity)
    {
        dbContext.Entry(entity).State = IsPersistent(entity) ? 
            EntityState.Modified : EntityState.Added;
        dbContext.SaveChanges();
    }

Answer 1

As you've already mentioned yourself, reattaching the user to your current context should solve the problem. The only other way I know of, would be to retrieve the object once again in your context based on the primary key value.