EF6: Multiple added entities may have the same primary key

Question

I've inherited a database and I need to insert data using EF6. I get the error:

DbUpdateException: Unable to determine the principal end of the 'POSModel.FK_KitMemberTaxRaw_KitMemberSaleReturnRaw_KitMemberSaleReturnRowId' relationship. Multiple added entities may have the same primary key. 

I deserialize XML to the POCO objects using DataContractSerializer. I'm using the object references from the xml document's structure to define the relationships. The POCO objects are generated using a t4 script provided from the NuGet package (which does not work with either deserializer well at all!)

I've decorated KitMemberTaxRaw like so:

[ForeignKey("KitMemberSaleReturnRaw")]
public virtual KitMemberSaleReturnRaw KitMemberSaleReturnRaw { get; set; }

[ForeignKey("KitMemberKitMemberSaleReturnRaw")]
public virtual KitMemberKitMemberSaleReturnRaw KitMemberKitMemberSaleReturnRaw { get; set; }

The KitMemberTaxRaw table may be joined to either table KitMemberKitMemberSaleReturnRaw or KitMemberSaleReturnRaw (but not both).

How does EF determine 'the principal end of the relationship'?

Answer 1

The issue turned out to be EF6 was not able to automatically understand a table with links to a parent and an optional grand parent. The navigation properties generated by the Microsoft provided template were correct but insufficient.

To cure the issue I manually created temporary primary keys for the relationship it did not understand.

Note: The DataContractSerializer class I used created the POCO objects creates an array for the instantiated navigation properties. I had to change the template to generate IList<> properties instead of ICollection<>. At run time there were errors because the array could not be dynamically resized.