Hi Kuba Cole,
OpenAccess currently provides an object reference to the related field e.g. CustomerAdress in your case. You can access it's Id using Customer.CustomerAddress.Id. In order to set this Id field directly though, there is currently a workaround for direct access to foreign key fields. It is discussed in the following KB article
. I must notice though that this workaround is only temporary and this process will be automated and the functionality usable via wizards in one of our next, post Q2 releases.
I hope the workaround works for you. If you require any additional clarifications, we are looking forward for your future feedback.
All the best,
the Telerik team