Can't get XAF/XPO association working as expected

Question

Here is the context:

In a XAF (Winforms) solution, we have a Production object which has 2 properties:

• string Description

• XPCollection Products

   [Persistent(@"PRODUCTION")]
   public partial class Production : XPLiteObject
   {
       long oid;
       [Key(true)]
       [Persistent(@"OID")]
       public long Oid
       {
           get { return oid; }
           set { SetPropertyValue<long>(nameof(Oid), ref oid, value); }
       }
       string description;
       [Size(80)]
       [Persistent(@"DESCRIPTION")]
       [DbType("VARCHAR2(80 CHAR)")]
       public string Description
       {
           get { return description; }
           set { SetPropertyValue<string>(nameof(Description), ref description, value); }
       }
       [Association(@"ProductReferencesProduction")]
       public XPCollection<Product> Products { get { return GetCollection<Product>(nameof(Products)); } }
   }
  

And a Product object with, among others properties:

• Production Production

   [Persistent(@"PRODUCT")]
   public partial class Product : XPLiteObject
   {
       long oid;
       [Key(true)]
       [Persistent(@"OID")]
       public long Oid
       {
           get { return oid; }
           set { SetPropertyValue<long>(nameof(Oid), ref oid, value); }
       }
       DateTime creation;
       [Persistent(@"CREATION")]
       public DateTime Creation
       {
           get { return creation; }
           set { SetPropertyValue<DateTime>(nameof(Creation), ref creation, value); }
       }
       DateTime modification;
       [Persistent(@"MODIFICATION")]
       public DateTime Modification
       {
           get { return modification; }
           set { SetPropertyValue<DateTime>(nameof(Modification), ref modification, value); }
       }
       string modificator;
       [Size(200)]
       [Persistent(@"MODIFICATOR")]
       [DbType("VARCHAR2(50 CHAR)")]
       public string Modificator
       {
           get { return modificator; }
           set { SetPropertyValue<string>(nameof(Modificateur), ref modificateur, value); }
       }
       Production production;
       [Persistent(@"PRODUCTION")]
       [Association(@"ProductReferencesProduction")]
       public Production Production
       {
           get { return production; }
           set { SetPropertyValue<Production>(nameof(Production), ref production, value); }
       }
   }
  

The problem is when we create a new Product inside a Production, it does not link them together. In the database, the field Production remains empty.

Any idea what we are missing?