My VSTO 3.0 Outlook addin doesn't load

vsto outlook-2007 outlook-addin
Wayne Kao picture Wayne Kao · Aug 25, 2009 · Viewed 7k times · Source

I'm trying to diagnose why my Outlook plugin written in C#/VSTO 3.0/VS 2008 doesn't load after being installed.

The plugin works awesomely on my development machine, which has Visual Studio 2008 installed. I can't expect all my users to have all the prerequisites though so I went through these steps to write an installer: http://msdn.microsoft.com/en-us/library/cc563937(loband).aspx

I installed the add-in on a fresh Windows XP SP 2 machine with a fresh install of Outlook 2007. It installs all the prereqs ok (.NET 3.5, VSTO 3.0 runtime, Windows Installer 3.1, 2007 PIAs). Outlook starts but the add-in isn't run. If I go to the Add-ins tab in the Trust Center, I see my add-in in the "Inactive Application Add-ins" section with the message "Not loaded. A runtime error occurred during the loading of the COM Add-in.".

Not sure how to find the specific error so I can fix it.

The reg keys look ok. Under HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Addins\BlahAddin I see Description, FriendlyName, LoadBehavior (set to 3 until it fails after which if becomes set to 2), and Manifest.

Tried the VSTO_SUPPRESSDISPLAYALERTS environment variable trick and then launched Outlook from the command line but no output came out.

I have remote debugging more or less working but I'm not sure what to look for. I don't see my DLL loaded when I attach to Outlook, but then again maybe managed DLLs don't show up the same way in VS.

Any other ideas on next steps I could follow to produce a specific error I can diagnose?

Answer

Wayne Kao picture Wayne Kao · Sep 18, 2009

Solved my problem after weeks of pain. The "Manifest" reg key was getting corrupted to some junk value during the setup build. It was a known Visual Studio bug that supposedly got fixed in Visual Studio 2008 SP 1, but apparently wasn't for me. Renaming the project name to be different from the plugin name fixed the problem. Random, huh?

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