Vista, Office Interop not working

Question

Does anyone know how to get the MS Office 2007 .NET C# Interop libraries to work with Vista?

I have a .NET C# application that I have setup to run as a Windows service. This program will open up a Word or Excel template depending on the situation and modify its contents and then save the document back out. All of this worked great when I was doing it on a Windows Server 2003 or XP machine using Office 2007. When I moved everything to a Server 2008 box, everything quit working. In Excel for example, I get a COM exception telling me that the Excel file cannot be opened when the file is clearly there and I can open it just fine when doing it manually. The windows service is running under the same user account that I log into the machine with and that account is an Administrator.

Does anyone have any idea what to do?

Answer 1

On Vista and Windows Server 2008, services run in something called Session0. Before Vista, regular programs would run in Session0 alongside services.

This means that Session0 has become a desktop-less wasteland where your services can't even access explorer.exe. I'm pretty sure the problem is that Office applications are expecting to be able to access a few components that are normally on the desktop.

Since Excel, Word, etc. are only supported on a desktop-ed session, you only have a few choices:

1. Set the Desktop checkbox in the LogOn tab of your Service's properties and pray that it appeases the Office gods. (It probably wont.)
   • After trying 1, go through your code and try and remove/work around anything that causes it to crash.
2. Use remoting/WCF to make a server that performs the interop work, and make your service communicate with it.
   • You'll need to have a logged in interactive user and the user needs to start the server application somehow. Perhaps best to use autostart.
   • You can try turning on Automatic login. http://support.microsoft.com/kb/324737
3. Try impersonating a Logged in user using CreateProcessAsUser and friends.
   • Note: I don't know how well this works unless a user is actually logged in, so it might not be any more useful than 2 above, and is much harder to pull off. (Needs P/Invoke)
4. Rewrite your program to use the OpenXML sdk or use something like SpreadsheetGear.

Answer 2

You should really avoiding running the Office clients as server side apps. Consider using xml as file format (xlsx for Office 2007, or using the Excel workbook xsd for (somewhat) older versions.) Then you would be freed from using the Excel API on the server.