How do I map this redundant parent-child relationship using Fluent API

Question

Any suggestions on how I can double-map this parent-child relationship, where the parent has a normal 1-many relationship (which is working), but then I need a direct 1:1,0 link from the parent to a particular child.

Public Class Source
    <Key()>
    Public Property SourceID As Int32

    Public Property SourceFields As List(Of SourceField)

    Public Property InboundMatchKeySourceFieldID As Nullable(Of Int32)
    Public Property InboundMatchKeySourceField As SourceField

And

Public Class SourceField
    <Key()>
    Public Property SourceFieldID As Int32

    Public Property SourceID As Int32

    Public Property Source As Source

This is the Parent/Child Mapping (Working)

    modelBuilder.Entity(Of Source).HasMany(
        Function(S) S.SourceFields
    ).WithRequired(
        Function(SF) SF.Source
    ).HasForeignKey(
        Function(SF) SF.SourceID
    )

This is my failed attempt at an additional direct mapping (Not Working):

modelBuilder.Entity(Of Source
    ).HasOptional(
        Function(S) S.InboundMatchKeySourceField
    ).WithRequired(
        Function(SF) SF.Source
    )

This yields me the 'MetaDataException':

Schema specified is not valid. Errors: The relationship '_____.Source_InboundMatchKeySourceField' was not loaded because the type '_____.SourceField' is not available.

score 0 · Answer 1 · answered May 15 '15 at 14:46

0

.WithRequired(...) returns a instance of ForeignKeyNavigationPropertyConfiguration. You need to map this relationship to a Key using the map Method, otherwise EF will try to create one for you.

so the code you are looking for is:

modelBuilder.Entity(Of Source
).HasOptional(
    Function(S) S.InboundMatchKeySourceField
).WithRequired(
    Function(SF) SF.Source
) _
.Map(Function (x) x.MapKey("InboundMatchKeySourceFieldID"))

answered May 15 '15 at 14:46

Chad Carisch

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Good suggestion, alas, I still get the same error message – Tom Halladay May 15 '15 at 17:49

score 0 · Answer 2 · answered May 19 '15 at 18:38

You can't use the same property SourceField.Source for both relationships.

There's ambiguity from Entity Framework's perspective:

If you set someSourceField.Source, does that mean someSourceField gets added to thatSource.SourceFields, or thatSource.InboundMatchKeySourceField gets set, or both?
What if someSource.InboundMatchKeySourceField.Source != someSource?

Perhaps you could create the second mapping without a navigation property and use validation to make sure SourceFields.Contains(InboundMatchKeySourceField) or thisSource.InboundMatchKeySourceField.Source == thisSource if needed:

modelBuilder.Entity(Of Source
    ).HasOptional(
        Function(S) S.InboundMatchKeySourceField
    ).WithRequired()

How do I map this redundant parent-child relationship using Fluent API

2 Answers2