In that scenario you would not have a reference to the Outlook 2007 PIA, you
would have one for the Outlook 2003 PIA. You would need to have installed
the Outlook 2003 PIA's either before installing Office 2007 or add them at
some other time. You can certainly have multiple versions of the PIA's
installed, I have both 2003 and 2007 on some of my dev machines and some of
my friends have PIA versions for Outlook 2000, 2002, 2003 and 2007 installed
on the same machines.

The official scenario is to develop 2 versions, one for 2003 and one for
2007. That would let the full support for each version be used. If you
develop using VSTO for an Outlook 2003 addin it will work on Outlook 2007
but of course then would not support the ribbon.

--
Ken Slovak
[MVP - Outlook]
http://www.slovaktech.com
Author: Absolute Beginner's Guide to Microsoft Office Outlook 2003
Reminder Manager, Extended Reminders, Attachment Options
http://www.slovaktech.com/products.htm


"Michael" wrote in message
...
Ahh... I suspected as much.

I am writing in C#. What would be the mechanics to get an Outlook 2007
reference in this scenario? The PIA's can only be installed on a system
with that version of Office, and you can only have one version of Outlook
installed at a time (if I understand correctly). Would I need two
development environments; one with Office 2003 to create the add-in using
the Outlook 2003 PIA and another with Office 2007 to change the reference?

If I didn't take this unsupported approach, would I instead have to
refactor my code into two add-ins (with a lot of common code), build each
on different build machines, and install the appropriate one based on the
version of Outlook installed?

Michael