Both VSTO and shared, shimmed addins are managed code and can be written in
C#.

It's much harder if not impossible to support both Outlook 2003 and 2007 in
a VSTO addin unless you decide not to support the ribbon in Outlook 2007.

There are workarounds for using the ribbon in shared addins even when
compiled as Outlook 2003 addins.

If using managed code and a shared addin you definitely should shim it to
give it it's own AppDomain so crashes or problems in other addins don't get
yours disabled.

--
Ken Slovak
[MVP - Outlook]
http://www.slovaktech.com
Author: Professional Programming Outlook 2007
Reminder Manager, Extended Reminders, Attachment Options
http://www.slovaktech.com/products.htm


"Joe Lakey" wrote in message
...
I am working on an Outlook add-in that has custom forms and interacts
with web services. The current version is a managed (C#.net) COM add-
in, but I am running into a number of issues, most involving other add-
ins. I'm looking into two possible solutions: using a COM shim and
using VSTO. My understanding is that with a COM shim, there is minimal
rewrite of existing code, but that VSTO would allow me to use managed
code. I am required to have only one codebase for both Outlook 2003
and 2007 (and possibly future versions). Any advice would be greatly
appreciated.