EF code first - add inverse propterty with optional element - entity-framework

Question

I have the following classes
public class Order {
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[Required]
public DateTime Date { get; set; }
[Required]
[MaxLength(100)]
public string From { get; set; }
public int? TreatGuestEntryID { get; set; }
[ForeignKey("TreatGuestEntryID")]
public TreatedGuestEntry TreatGuestEntry { get; set; }
...
public class TreatedGuestEntry {
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[MaxLength(200)]
public string Company { get; set; }
public string TypeOfTreat { get; set; }
This works as expected - in my Orders table it creates the foreign key.
Now I want to add an inverse property in TreatedGuestEntry for the order.
The best (at least somehow working) result I get when I add
modelBuilder.Entity<TreatedGuestEntry>()
.HasOptional(a => a.Order)
.WithOptionalDependent(a => a.TreatGuestEntry)
.Map(a=>a.MapKey("TreatGuestEntryID"));
and further rename the key of TreatedGuestEntry to TreatGuestEntryID.
But I get no relation in the database and also TreatGuestEntryID in the table Order is no longer a key (FK).
My approach in simple words:
In my Order I want an optional TreatedGuestEntry (and I need access to the foreign key) - and further in the related TreatedGuestEntry I want to access the Order.

Answer 1

In your case, the FK TreatGuestEntryID is not a PK, it means that it is a 1:n relationship. So, you have to put a Collection of Order on the other side:
public class Order
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[Required]
public DateTime Date { get; set; }
[Required]
[MaxLength(100)]
public string From { get; set; }
public int? TreatGuestEntryID { get; set; }
public TreatedGuestEntry TreatGuestEntry { get; set; }
}
public class TreatedGuestEntry
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int ID { get; set; }
[MaxLength(200)]
public string Company { get; set; }
public string TypeOfTreat { get; set; }
public ICollection<Order> Orders { get; set; }
}
Mapping:
modelBuilder.Entity<Order>()
.HasOptional(i => i.TreatGuestEntry)
.WithMany(i => i.Orders)
.HasForeignKey(i => i.TreatGuestEntryID)
.WillCascadeOnDelete(false);
Generated Migration:
CreateTable(
"dbo.Orders",
c => new
{
ID = c.Int(nullable: false, identity: true),
Date = c.DateTime(nullable: false),
From = c.String(nullable: false, maxLength: 100),
TreatGuestEntryID = c.Int(),
})
.PrimaryKey(t => t.ID)
.ForeignKey("dbo.TreatedGuestEntries", t => t.TreatGuestEntryID)
.Index(t => t.TreatGuestEntryID);
CreateTable(
"dbo.TreatedGuestEntries",
c => new
{
ID = c.Int(nullable: false, identity: true),
Company = c.String(maxLength: 200),
TypeOfTreat = c.String(),
})
.PrimaryKey(t => t.ID);