ajlampman ajlampman - 1 year ago 112
Vb.net Question

VSTO Addin for Outlook won't work

I've seen tons of posts and sites that address this issue. I've tried every solution I've found but none of them work (I've been trying to figure this out for days now). I have seen many posts with the same exact sounding issue, but either the solution didn't work for me or isn't applicable. With that said...

I have an add-in for Outlook 2007 that is intended to add text to the an email's title and body. It is installed for all users using an .msi file. There is an older version that I deployed last year that works fine. The new version I created has only a few minor input/output changes, nothing major. This new version works perfectly on my development computer in both debug from Visual Studio and from an actual install. However, I can't get it to work on a non-development computer. Here are the details on the program and target computer (development computer and target computer details are the same other than the fact that the target computer doesn't have Visual Studio):

-Using Visual Studio Professional 2013
-Written in Visual Basic
-Target Framework is .NET 4.0
-The add-in is only run once the "send" button on an email is clicked.
-Outlook version is Outlook 2007
-Operating system is Windows 7 Enterprise SP1 32-bit

The problem is that the add-in won't load on the target computer(yes, I know, a bazillion other people have had the same issue). As I said previously, it works fine on my computer in both debug and installed versions. This made me think that the other computer is missing something, so I tried installing the .NET 4.0 framework onto the target computer but it told me that it was already installed. I ran through everything I could think of to get it to work with no avail. Here's how it behaves:

-Installs fine with no errors.
-HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/Office/Outlook/Addins/EmailMarkTool/LoadBehavior = 3 after installation.
-Outlook opens with no apparent errors.
-LoadBehavior = 0 immediately after Outlook is opened.
-Shows up in the Add-ins under "Inactive Application Add-ins."
-Never shows up under "Disabled Add-ins."
-In the "COM Add-Ins" dialog where I can check which add-ins to use, it shows the correct directory and the Load Behavior is "Unloaded."
-The add-in can be checked. When I click "OK" I don't get any errors. When I go back to the Add-ins, it is unchecked and "Unloaded" again.
-Setting the LoadBehavior to 3 doesn't help because it goes back to 0 as soon as Outlook is started again.
-I inserted a try-catch block into the New() function of the add-in that has a MsgBox pop-up and a Throw.
-I get absolutely no errors anywhere.
-No log file is generated.

I have tried uninstalling, rebuilding, and reinstalling multiple times all with the same result. I just can't figure out why it will work on my development computer but not the target computer. Thanks for reading all of this. I know it's a lot, but I needed to get the details out. Thanks in advance for any input!

[UPDATE]: I just created a brand new minimal add-in just to test if it would work but got the same results.

Answer Source

I found the problem!

The problem may be unique to Outlook 2007. It turns out Microsoft Office 2007 SP1 and SP2 had a bug that prevented it from running VSTO addins. Microsoft released a hotfix that fixes this issue (https://support.microsoft.com/en-us/kb/976477). This was added in to the release of Microsoft Office SP3. However, to activate the fix, a new registry flag must be created but that isn't automatically done with the fix, making the fix useless until you manually activate it (instructions and download here). So...

To enable VSTO addins in Outlook 2007, you have to add a subkey to this registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\12.0\Common\General\ and add a DWORD "EnableLocalMachineVSTO" with the value set to 1.

I did this, restarted the computer for good measure, installed my addin for the 23rd time, and it installed and ran perfectly! I'm not sure how previous versions worked, though. It's possible that our system admins removed that subkey in an effort to bolster security at some point.

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