Question

I’m having an odd problem, I can’t get an object from the DB and then reattach it. I have written code like this for other projects but for some odd reason it throws the following error in this application:

System.InvalidOperationException: The EntityKey property can only be set when the current value of the property is null.

here is my code:

        Entities.Customer customer;
        using (var context = new XXEntities())
        {
            IQueryable<Entities.Customer> query = from a in context.Customers select a;
                query = query.Where(c => c.CODE == "003046");
            customer = query.ToList()[0];
        }


        using (var context = new XXEntities())
        {
            context.Customers.AddObject(customer);
            context.SaveChanges();
        }

Answer 1

In the 2nd block,

    using (var context = new XXEntities())
    {
      //context.Customers.AddObject(customer);
        context.Customers.Attach(customer);  
        context.SaveChanges();
    }

EntitySet.Add() means add a new object. You want to add an existing object.