Entities in '' participate in the '' relationship. 0 related '' were found. 1 '' is expected

Question

I've seen this question posted previously but I've implemented all the accepted answers in my code and I'm still getting the error.

I have a number of classes (Client, Supplier etc) that each have a List(of Address) so each class can have a number of different addresses. These classes are not inherited from each other but implement IAddresses which points to the ID, ClassType and List(of Address) properties. (My code is in VB but I understand enough C# that if you offer solutions in C# they will be useful).

The problem I'm having is that when I try to add a new address to a Client, I get the following error: Entities in 'DataContext.Addresses' participate in the 'Supplier_Addresses' relationship. 0 related 'Supplier_Addresses_Source' were found. 1 'Supplier_Addresses_Source' is expected. Entities in 'DataContext.Addresses' participate in the 'Supplier_Addresses' relationship. 0 related 'Supplier_Addresses_Source' were found. 1 'Supplier_Addresses_Source' is expected.

My Supplier configurations:

Public Class SupplierConfiguration
    Inherits EntityTypeConfiguration(Of Supplier)
    Public Sub New()
 
        [Property](Function(x) x.Email).HasMaxLength(200)
        [Property](Function(x) x.GivenName).HasMaxLength(50).IsRequired()
        [Property](Function(x) x.PhoneH).HasMaxLength(20)
        [Property](Function(x) x.PhoneM).HasMaxLength(20)
        [Property](Function(x) x.Status).IsRequired()
        [Property](Function(x) x.Surname).HasMaxLength(50).IsRequired()
        [Property](Function(x) x.Title).HasMaxLength(5)
        HasMany(Function(x) x.Comments).WithRequired(Function(x) x.Parent)
        HasMany(Function(x) x.Addresses).WithRequired(Function(x) x.Parent)
        Ignore(Function(x) x.ParentType)
    End Sub
End Class

My Client Configurations:

Public Class ClientConfiguration
    Inherits EntityTypeConfiguration(Of Client)
    Public Sub New()
        [Property](Function(x) x.Alert).IsMaxLength()
        [Property](Function(x) x.Email).HasMaxLength(200)
        [Property](Function(x) x.EntityName).HasMaxLength(100).IsRequired()
        [Property](Function(x) x.Status).IsRequired()
        HasMany(Function(x) x.Addresses).WithRequired(Function(x) x.Parent)
        HasMany(Function(x) x.Comments).WithRequired(Function(x) x.Parent)
        HasMany(Function(x) x.Invoices).WithOptional(Function(x) x.Client)
        HasMany(Function(x) x.Jobs).WithRequired(Function(x) x.Client)
        Ignore(Function(x) x.ParentType)
    End Sub
 
End Class

I'm using the Repository Pattern for persistence, and here is my UnitOfWork class:

Imports System.Data.Entity
 
Public Class UnitOfWork
    Implements IUnitOfWork
    Private ReadOnly Property _context As DataContext
    Private _Addresses As AddressRepository
    Private _Clients As ClientRepository
    Private _Comments As CommentRepository
    Private _Suppliers As SupplierRepository
    Public ReadOnly Property Addresses As IAddressRepository Implements IUnitOfWork.Addresses
        Get
            Return _Addresses
        End Get
    End Property
    Public ReadOnly Property Clients As IClientRepository Implements IUnitOfWork.Clients
        Get
            Return _Clients
        End Get
    End Property
    Public ReadOnly Property Comments As ICommentRepository Implements IUnitOfWork.Comments
        Get
            Return _Comments
        End Get
    End Property
    Public ReadOnly Property Suppliers As ISupplierRepository Implements IUnitOfWork.Suppliers
        Get
            Return _Suppliers
        End Get
    End Property
    Public Sub New(context As DataContext)
        _context = context
        _Addresses = New AddressRepository(_context)
        _Clients = New ClientRepository(_context)
        _Comments = New CommentRepository(_context)
        _Suppliers = New SupplierRepository(_context)
    End Sub
    Public Function Context() As DbContext
        Return _context
    End Function
    Public Function Complete() As Integer Implements IUnitOfWork.Complete
        Dim log As String = vbNullString
        Dim errors = _context.GetValidationErrors
        If errors.Count > 0 Then Stop
        Dim ReturnValue As Integer
        Try
            ReturnValue = _context.SaveChanges
        Catch ex As System.Data.Entity.Validation.DbEntityValidationException
            ShowException(ex)
            ReturnValue = 0
        Catch ex2 As Exception
            ShowException(ex2)
            ReturnValue = 0
 
        End Try
        Return ReturnValue
    End Function
 
    Public Sub Dispose() Implements IDisposable.Dispose
        _context.Dispose()
    End Sub
End Class

My Supplier class:

Public Class Supplier
    Implements IAddresses, IComments
    Property ID As Integer Implements IAddresses.ID, IComments.ID
    Property Email As String
    Property EntityName As String
    Property GivenName As String
    Property PhoneH As String
    Property PhoneM As String
    Property Status As eSupplierStatus
    Property Surname As String
    Property Title As String
 
    Property Addresses As Addresses Implements IAddresses.Addresses
    Property Comments As Comments Implements IComments.Comments

    ReadOnly Property ParentType As String Implements IComments.ParentType, IAddresses.ParentType
        Get
            Return Me.GetType.Name
        End Get
    End Property
 
End Class

I can't understand why I'm trying to save an address to the Client class but EF wants a Supplier class. They should be completely independent?

Answer 1

EF created non-nullable FK fields on the Addresses table: Client_ID, Supplier_ID etc, so when saving an address for a Client the null value for Supplier_ID threw the error. Solution is to change the Client and Supplier configurations to WithOptional instead of WithRequired

HasMany(Function(x) x.Addresses).WithOptional(Function(x) x.Parent)

_{(Addition to the question moved to a proper answer)}