[TestMethod]
    public void can_add_lineItem_to_new_detached_order() {
 
      var mgr = new NorthwindManager(false /* = disconnected */);
 
      // Pretend we retrieved an existing product
      var prod = new Product
                   {
                     ProductID = 42,
                     ProductName = "Foo",
                   };
      mgr.AttachEntity(prod); // attaches as "unchanged"
 
      var order = new Order(); // not yet associated with a manager 

      // Create new lineitem which is immediately added to mgr
      // because the assignment of its Product pulls it into
      // the mgr of the "Prod" entity.
      // The act of adding this lineitem to the lineitems of the order
      // causes the new order to be pulled into the mgr as well.
      // All this confirmed in subsequent Asserts.
      order.OrderDetails.Add(new OrderDetail{Product = prod}); 

      Assert.AreEqual(order.EntityAspect.EntityState, EntityState.Added);
      Assert.AreEqual(1, order.OrderDetails.Count); 

      var lineItem = order.OrderDetails.First(); // get the new OrderDetail
 
      Assert.AreEqual(lineItem.EntityAspect.EntityState, EntityState.Added);
      Assert.AreSame(lineItem.Product, prod);
      Assert.AreSame(order.EntityAspect.EntityManager, lineItem.EntityAspect.EntityManager);
      Assert.AreSame(order.EntityAspect.EntityManager, prod.EntityAspect.EntityManager);
 
    }

First look at the DebugLog to see if an IdGenerator is being discovered – if not – bingo

If so, have him send the IdGenerator that he is using., or have him debug into his IdGenerator GetRealIdMap method.

Or

He may be using autoincrement ids and only sending part of the graph – hence the hint about

    If you are using auto-incrementing ids check that the FixupTempIds SaveOption is set to InSaveListOnly