An object with the same key already exists in the ObjectStateManager...

I have an entity model with (among others) following four entities:

QCompany: - PK_Company - CompanyName - QAddress - a collection of addresses

QAddress: - PK_Address - Streetname - QZipCode - QAddressType

QAddressType: - PK_AddressType - Description

QZipCode: - PK_ZipCode - ZipCode - Maildepot

I try to do the following:

I have an existing company that i want to add new addresses to.

QAddress addr = new QAddress { .... };

I use WCF so I have to send the new entityobject addr to the wcf-service. There I try to add the address to the context.

_context.AddToQAddress(addr); _context.SaveChanges();

Then I get an error: An object with the same key already exists in the ObjectStateManager.

So I try to attach the address

_context.Attach(addr);

But then i get the following error: Object entity key i null.....

My next move was to add the addresses to the company directly: QAddress[] addresses = new QAddresses {addr}; company.QAddress = addresses;

and attach the updated company to the context.

_context.Attach(company);

But the same errors occur every time.

I'm going crazy. I don't seem to find a way to solve this problem.

Can anyone help?

ansaurus