GetNewObjectKey() returning empty

Hello.

I'm adding some documents via DI API. Actually it's 3 documents and i'm adding them using transaction control.

I need the DocEntry of the second document but after Document.Add(), the method Company.GetNewObjectKey() returns empty.

When I commit the transaction, it succesfully create the documents.

What am I doing wrong?

Code sample:

if (lDocumento.Add() != 0)                    {                        return false;                    }
DataSource.SetValue(DataSourceUIDs.CodigoPedidoVenda, 0, mAddOn.Connection.Database.GetNewObjectKey()); //<= Returns empty