VSTO Outlook Add-in Debug errors even for simple HelloWorld add-in


Recently I have been developing an Outlook addin utilising a Model View Controller Architecture and Mocks.

This architecture has given me a great deal of testability of my addin without having to run Outlook.  The downside of this of course is that today when I went to run the Outlook Addin for real it didn’t work.

I pressed “run”, Outlook started, then the IDE went out of debug.  No breakpoints hit, no errors, no nothing.  Great!

The False Solution

As it turns out the “Windows Live Toolbar” (whose indexing I use all the time in Outlook) uses .net Framework 1.1.  It internally forces Outlook addins to use 1.1, which means my 2.0 addin failed to work.  Not fun.

I uninstalled the Windows Live Toolbar and now I can debug successfully.

I guess this highlights the fact that you still need to do testing of the real application as well as.

The post that helped me work out the problem is here:

VSTO Outlook Add-in Debug errors even for simple HelloWorld add-in – MSDN Forums

The Real Solution – An update to the original post

This is happening again!  I’d re-uninstall the Windows Live toolbar if I could but it’s not there anymore!

As it turns out that somehow my addin had become “disabled”.  Apparently if one addin is “disabled”, all will be disabled.  Re – Enabling Addins (or un-disabling) has to be done from the highly intuitive location of the Outlook checkbox.

The steps I took.

1. Go into Help->About and click on the “Disabled Items…” button.  Reenable the addin.


2. Go into Tools->Options->Other->Advanced Options->Com Addins.  Remove the Addin


3. Quit outlook, then check task manager and ensure “OUTLOOK.EXE” is not running.  If it is, “End Process” it.

4. You should now be able to debug addins again.


3 responses »

  1. Hi,
    I am facing the debug issue. Try to fix as mentioned above but i can’t find “Com Addins” in Advanced Options. I am using outlook 2007.
    Please let me know how to resolve now.

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