Question

Person has two similar tables, difference is that each person has only one record in PersonPreference table, but can have many in PersonRoles table. Both PersonPreference and PersonRole have the same primary and foreign key (Person_ID):

<Table("Person")> _
Public Class Person
    <Key()> _
    Public Property Person_ID As Integer
    Public Property Name As String

    Public Overridable Property PersonPreference As PersonPreference
    Public Overridable Property PersonRoles As ObservableCollection(Of PersonRole)
End Class

<Table("PersonPreference")> _
Public Class PersonPreference
    <Key()> _
    Public Property Person_ID As Integer
    Public Property Car As String
    Public Property Color As String
End Class

<Table("PersonRole")> _
Public Class PersonRole
    <Key()> _
    Public Property Person_ID As Integer
    Public Property Role As String
End Class

Public Class PersonMap
    Inherits EntityTypeConfiguration(Of Person)

    Public Sub New()
        Me.HasRequired(Function(t) t.PersonPreference).WithRequiredPrincipal()
        Me.HasRequired(Function(t) t.PersonRoles).WithRequiredPrincipal()
    End Sub

End Class

Is there a way of saving the person roles as it is the code (without adding the Roles table) or there need to be modifications (primary key on PersonRoles table – I have tried making composite key in PersonRoles table, but that did not work)?

Answer 1

It is not necessary to have a Role table but you need to have a composite key in PersonRole table. I not familiar with VB.net so hope you can convert this into VB.net.

public class Person
{
    public int Id { get; set; }

    public string Name { get; set; }

    public virtual ICollection<PersonRole> PersonRoles { get; set; }

    //other properties
}

public class PersonContext : DbContext
{
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Person>().HasMany(p => p.PersonRoles).
          WithRequired().HasForeignKey(r => r.PersonId);

        modelBuilder.Entity<PersonRole>().HasKey(r => new {r.PersonId, r.Role});
    }

    public DbSet<Person> Persons { get; set; }
}

Here is an example

var ctx = new PersonContext();

var person = new Person {Name = "Foo"};
person.PersonRoles = new List<PersonRole>() 
      { new PersonRole { Role = "a" }, new PersonRole { Role = "b" } };

ctx.Persons.Add(person);

ctx.SaveChanges();