MVC + LINQ To SQL Model Binding - Saving A Complex Child Object After Post

I have a "Create New Employee" ASP.Net MVC form. My complex object is an Employee and an Employee has an Address, which is another Complex object. On my View/Form I collect all required values for both the Employee and the Address. I'm using the bound HTML helpers such as: Html.TextBoxFor(model => model.EmployeeAddress.StreetName)

AND

Html.TextBoxFor(model => model.NewEmployee.FirstName)

This is all working beautifully well. Model binding is working like a dream, both server side and client side validation using DataAnnotations is working beautifully well and I am nicely receiving my populated complex objects as expected in the Controller.. Now I'm trying to save.. The Employee should always be newly created, because its an "Add New Employee" form. But sometimes the Address is an existing Address and I don't want to insert another one. Rather, I just want to link the Employee to the existing AddressID of the one that already exists in the database.

So I wrote a nifty GetExistingOrCreateNewAddress(Address PostedAddress) method which works great so I end up with the correct Address to use and link to the about to be saved Employee object. This is all happening in the same DataContext, so no problems there..

BUT even when I link the about to be saved Employee object to an existing Address, on save a new/empty Address row is created in my Addresses table. Even though the newly created Employee does link correctly to the existing Address I told it to! Why is it so??? And how can I save the new Employee without LINQ automatically creating a blank Address for me. Because I'm explicitly specifying an existing Address it should be linked to instead!

[HttpPost]
public ActionResult CreateEmployee(EmployeeDetailsViewModel NewEmployeeDetails)
{
if (ModelState.IsValid)
{
EmployeeRepository ER = new EmployeeeRepository();
// Fetch or Create the appropriate Address object for what has been entered
Address ActualAddress = ER.GetExistingOrCreateNewAddress(NewEmployeeDetails.EnteredAddress);
// Link this Address to the "about to be saved" Employee
NewEmployeeDetails.Employee.Address = ActualAddress;
// Lock it in..
ER.SaveNewEmployee(NewEmployeeDetails.Employee);