How can I tell if a VSTO Add-in is loaded?

Question

I'm working on a VSTO add-in for Outlook that, if another custom VSTO is loaded, will perform a specific action. How would I determine if that VSTO is loaded? I've not delved too far into COM as of yet other than writing a number of add-ins.

Answer 1

You can check the key:

"HKLM\\Software\\Microsoft\\Office\\Outlook\\Addins[YourAddInName]"

in the registry.

Existence of the key means that the AddIn is installed. You can also read the value LoadBehaviour under the above key, the value 3 means that the addin is loaded/to be loaded normally. The value 2 means that the addin has problems.