Collection property not properly added to parent on save

Collection property not properly added to parent on save

Look at the following code example.
What it does:
Iterates a bunch of customers. If it already knows the customer, it
retrieves the existing database object for that customer (this is the
problem-ridden part). Otherwise, it creates a new object (this works
fine).
All loans where the social security number matches (CPR) will be added to
the new or existing customer.
The problem: it works for new customer objects, but when I retrieve an
existing customer object, the loans lose their relation to the customer
when saved (CustomerID = null). They are still saved to the database.
Any ideas?
protected void BuildCustomerData()
{
Console.WriteLine(" Starting the customer build.");
var counter = 0;
var recycleCount = 100;
var reportingCount = 100;
var sTime = DateTime.Now;
var q = from c in db.IntermediaryRkos
select c.CPR;
var distincts = q.Distinct().ToArray();
var numbersToProcess = distincts.Count();
Console.WriteLine(" Identified " + numbersToProcess + " customers. "
+ (DateTime.Now - sTime).TotalSeconds);
foreach (var item in distincts)
{
var loans = from c in db.IntermediaryRkos
where c.CPR == item
select c;
var existing = db.Customers.Where(x => x.CPR ==
item).FirstOrDefault();
if (existing != null)
{
this.GenerateLoanListFor(existing, loans);
db.Entry(existing).State = System.Data.EntityState.Modified;
}
else
{
var customer = new Customer
{
CPR = item,
};
this.GenerateLoanListFor(customer, loans);
db.Customers.Add(customer);
db.Entry(customer).State = System.Data.EntityState.Added;
}
counter++;
if (counter % recycleCount == 0)
{
this.SaveAndRecycleContext();
}
if (counter % reportingCount == 0)
{
Console.WriteLine(" Processed " + counter + " customers of
" + numbersToProcess + ".");
}
}
db.SaveChanges();
}
protected void GenerateLoanListFor(Customer customer,
IQueryable<IntermediaryRko> loans)
{
customer.Loans = new List<Loan>();
foreach (var item in loans.Where(x => x.DebtPrefix ==
"SomeCategory").ToList())
{
var transformed = StudentLoanMap.CreateFrom(item);
customer.Loans.Add(transformed);
db.Entry(transformed).State = System.Data.EntityState.Added;
}
}