How do I map a redundant relationship in Entity Framework (EF6) Code-First

Question

We're trying to map some redundant relationships, and have been unable to figure out the perfect combination of foreign keys, navigational properties, and ModelBuilder statements.

This is a simplified example; I realize that some people might recommend changing the table structure as a whole, but we've encountered several situations where we need this type of configuration.

Simplified Diagram:

POCO Classes:

Public Class Customer
    <Key, Required>
    Public Property CustomerID As Int32

    Public Property Contacts As List(of Contact)

    Public Property PrimaryContact As PrimaryContact


Public Class Contact

    <Key, Required>
    Public Property ContactID As Int32

    <Required>
    Public Property CustomerID As Int32

    Public Property Customer As Customer

    Public Property PrimaryContact As PrimaryContact



Public Class PrimaryContact

    <Key, Required>
    Public Property CustomerID As Int32

    <Required>
    Public Property ContactID As Int32

    Public Property Customer as Customer

    Public Property Contact as Contact

Model Builder Attempt #1:

modelBuilder.Entity(Of Customer
).HasOptional(Function(C) C.PrimaryContact
).WithRequired(Function(PC) PC.Customer)

modelBuilder.Entity(Of Contact
).HasOptional(Function(C) C.PrimaryContact
).WithRequired(Function(PC) PC.Contact)

Usage:

Dim NewCustomer As Customer   'Assigned Elsewhere'
Dim NewContact As Contact     'Assigned Elsewhere'

NewCustomer.PrimaryContact =
    New PrimaryContact With {
        .Contact = NewContact 
    }

The Problems:

Our problems lie with the PrimaryContact table and relationships/navigational properties.

The current problem is that NewCustomer.PrimaryContact.Customer has no reference after this assignment.

There is a secondary problem where even if we manually assign NewCustomer.PrimaryContact.Customer = Customer , there is a valid reference, but EF does not wire up the ContactID on the insert

insert into "[SCHEMA]"."PRIMARYCONTACTS"("CUSTOMERID", "CONTACTID")
values (:p0, :p1)

-- :p0: '197467' (Type = Int32)

-- :p1: '0' (Type = Int32)

-- Executing at 9/1/2015 2:57:45 PM -04:00

-- Failed in 514 ms with error: ORA-02291: integrity constraint ([SCHEMA].PRIMARYCONTACTS_FK2) violated - parent key not found

Solutions!?

What advice do you have on how to properly configure the entities, or change the ModelBuilder mapping so that these entities and relationships function as we expect them to.

Answer 1

Upon further brainstorming, I realized that the navigational property from Contacts to PrimaryContact would never actually be useful. It turns out it was not useful and actually the culprit. When I removed it and the corresponding ModelBuilder code, everything started working

POCO Class

Public Class Contact

    <Key, Required>
    Public Property ContactID As Int32

    <Required>
    Public Property CustomerID As Int32

    Public Property Customer As Customer

    '-------------------- REMOVED  --------------------'
    '                                                  '
    ' Public Property PrimaryContact As PrimaryContact '
    '                                                  '
    '-------------------- REMOVED  --------------------'

Model Builder

modelBuilder.Entity(Of Customer
).HasOptional(Function(C) C.PrimaryContact
).WithRequired(Function(PC) PC.Customer)

'------------------ REMOVED  ------------------'
'                                              '        
' modelBuilder.Entity(Of Contact               '
' ).HasOptional(Function(C) C.PrimaryContact   '
' ).WithRequired(Function(PC) PC.Contact)      '
'                                              '
'------------------ REMOVED  ------------------'