How to debug Office add-in running in Citrix environment?

Question

I have a VSTO-based PowerPoint add-in that runs fine on Office 2007 and Office 2010. I have users running this add-in every day, day-in, day-out.

I'm now working with a new client that uses Citrix for their desktops. I've never really understood exactly how Citrix works, but it appears that no-one has locally-installed software - they just run everything off the Citrix box. It's a very locked-down environment. They use Office 2010 and what appears to be Vista.

Anyway, my add-in is exhibiting strange behavior in this environment. Simply clicking one of my buttons on the ribbon sometimes gives an error (if the "Show addin user interface errors" setting is ON). The error says "An error occurred when calling the callback "ButtonClick".

Other times, clicking the button appears to have no effect at all (although I suspect that it's actually starting to do something and then crapping out before displaying any messages).

I'm confused, because (a) it works elsewhere, and (b) I catch and report exceptions in all my button-click handlers, so I would expect to see an error reported.

Because the environment is so locked down, and it takes literally weeks to get a new version of my add-in rolled out, I don't know how to diagnose this.

Any ideas?

Answer 1

Have you ever used RDP to remote into another Windows machine? To all intents you can consider Citrix to be a much fancier version of RDP. So you have a bunch of servers where users run their apps and desktops, and they connect remotely to them using HDX instead of RDP.

Your customer could be using XenApp or XenDesktop. In XenApp the users run their sessions on Windows 2008 R2 servers, with multiple users sharing each server. XenDesktop is similar except instead of connecting to a server OS, the user connects to their own dedicated workstation image. At a guess your customer is probably using XenDesktop since you say they are running on "Vista".

Diagnosing your problem is going to be tricky without access to a Citrix environment. For my debugging I'll generally install the remote debugging agent on the Citrix machine and debug remotely from my workstation. Occasionally I'll use Windbg or Visual Studio installed directly on the Citrix machine. If your customer is willing to give you access to their environment you can try this.

Other options include:

• Add diagnostic tracing to your product.
• Citrix provides some compatibility testing services, see: http://citrix.com/partner-programs/citrix-ready/test.html

As to what might actually be going wrong, Citrix does a range of hooking that can cause unexpected behaviour. For XenApp in particular the multi-monitor hooking is the main cause of things going wrong (I am not sure if this applies to XenDesktop as well). If you do a Google search on "citrix disable hooks" you will find a range of links that describe how to disable hooks using the registry. Disabling the hooks in this way certainly works for XenApp. I am not so familiar with XenDesktop, so I don't know if the same techniques apply. I'd certainly recommend trying disabling hooking for PowerPoint to see if your issues go away.