Hi, I need to save two records on a "primary" object,, 1 record related to some child BOs and the 2nd record to another childs.

Hi Fabian,

Yes, you are correct about the BO.RegisterForeinKey() method.  For a clear explanation check this Post by Trent where it is explained much better.

how I can set that 1st I like to save the "Invoice" BO and then "Payment" BO to make it the 2nd register every time?

Well when using the BO.RegisterForeinKey() method, SF will take care of that for you, not matter which BO triggers the saving, it will go up to the parent bo to grab the PK.  But in your case, it would be better for you to manage this logic yourself, create your own Save method using a BusinesLayer Transaction so you can have full control on how information is saved.

Once you have this done, you will be amazed on how powerful and flexible SF Business Objects are.  Using the 2 BO instances will allow you to handle each record based on their transaction type (ex: Invoice or Payment) so you will always know which record you are managing.

Edhy Rijo