Hi Rich,
Yes.
As pointed out it's not the language that's the issue with writing an AddIn - C+,C#, VB.net - anything that can create a valid DLL. In my experience writing AddIns is more about understanding the EA API and dealing with the quirks of windows.
BTW: These days I write nearly all my AddIns in VB.Net unless my customer specifically wants another language, although I'd probably draw the line at doing it in assembly language these days!
If it would help I'm sure I can provide some example VB.net projects including installers - what type of stuff are you trying to do?
Re the error, 800401F3 that is nothing to do with the language; the error message translates to
Invalid class string, so this looks like your AddIn DLL isn't registered or name is not correct. Suggest you download my free
Installation Inspector as that may provide a bit of information. V5 of the installer is in
Beta but may be more useful as it includes registry search functions that may help find any mismatch between class name and the class names in your dll file.
I also have some information/examples on registration/installation on the public part of my
tools site that may be of interest. As suggested by Uffe Wix works fine and worth getting a good working template sorted early on.
And as you've probably guessed there are plenty of experts on the forum always ready to help.
Adrian