How to import contacts into Outlook from a CSV file (including UID)

Question

I have an external database which stores my reference contact addresses (first name, last name, e-mail, phone number, etc.) and I would like to periodically import the data into Outlook (standalone, not via Exchange server).

There are numerous ways to import data (e.g. through CSV or vCard files), but before trying to implement this, I would like to know if I can make sure that my contacts will be properly merged with the existing ones.

If I assign a UID to every contact in a vCard file, will Outlook properly merge the changes when I repeatedly import the same contact again?

And how would I best automate the import from an external C# program?