EF Relationships vs Bidirectional Relationships in Apple Core Data

Question

I have the Database Specification for the application, that was created previously for iOS, and which used Apple Core Data as an ORM, so that all the relationships between tables there are bidirectional.

Do I need to do the same in Entity Framework (bidirectional relationships, which in most case are impossible to implement), or may I just use typical (One-to-One, Many-to-One, Many-to-Many) relationships and they will work the same way as bidirectional in Apple Core Data?

Answer 1

You make a mistake in you reasoning. You confuse the database configuration with the ORM configuration. When there is a one to many relation between a parent and a child table, the child table will hold a foreign key to the parent table. The parent table wil not have any field that relates to the child table.

When defining this relation using Code First you are free to implement it as:

Public Class Parent
    Public Property Id as Integer
    Public Overridable Property Children as ICollection(Of Child)
End Class

Public Class Child
   Public Property Id as Integer
   Public Property ParentId as Integer
   Public Overridable Property Parent as Parent
End Class

Or

Public Class Parent
    Public Property Id as Integer
End Class

Public Class Child
   Public Property Id as Integer
   Public Property ParentId as Integer
   Public Overridable Property Parent as Parent
End Class

Or

Public Class Parent
    Public Property Id as Integer
    Public Overridable Property Children as ICollection(Of Child)
End Class

Public Class Child
   Public Property Id as Integer
   Public Property ParentId as Integer
End Class