Thursday, December 04, 2008

Office 2003 Addin using Visual Studio Add-in (Extensibility) Project

A while back I had to write an add-in to Microsoft Office 2003 for a client and ran into numerous issues during both the development and the deployment of the add-in. Thought I should post it here in hopes that someone may find it useful.

I use Visual Studio 2005 Standard (I know, I know Visual Studio 2008 is out but I develop Pro/Toolkit and SolidWorks API applications too and am not sure if the upgrade is a simple recompile and link, so have not upgraded.), so in order to develop Microsoft Office 2003 Add-ins I had two options:

  • Use the Visual Studio Add-in Template under the "Extensibility" Project Type.
  • Use Visual Studio 2005 Tools for Microsoft Office 2003 (VSTO)
There is a good comparison of these two choices at CodeProject. I have a few additional points to note here that may influence your choice:
  • Using Visual Studio Add-in Template
    • DEVELOPMENT: Writing code for the add-in gets very clunky. The following is a sample excerpt:
      using Microsoft.Office.Core;
      using nsWord = Microsoft.Office.Interop.Word;

      nsWord.ApplicationClass office_app;

      public void OnConnection(object application, Extensibility.ext_ConnectMode connectMode, object addInInst, ref System.Array custom)
                  applicationObject = application;
                  addInInstance = addInInst;
                  if (connectMode != Extensibility.ext_ConnectMode.ext_cm_Startup)
                      OnStartupComplete(ref custom);
                  /// which office app is "application"
                  if (application is nsWord.Application)
                      office_app = (nsWord.ApplicationClass)application;
                      //if (logger.IsInfoEnabled) { logger.Info("host app is Word"); }

      As can be seen from the last few lines, to determine the Office Application that the add-in is loaded in is an equivalence test (using if-else or switch-case or some similar). I know this is not a good solution, but I don't have anything better (if someone has a better suggestion I would really appreciate the tip.

      Even if I got beyond that I am still casting the 'object application' to 'Microsoft.Office.Interop.Word'. I guess I could have used inheritance to pass 'application' to a sub-class that would deal with the specific Office Application, but I was surprised to find that you could not simply query for the Office App Type.
    • DEPLOYMENT: Deploying the Shared Add-in requires a bunch of updates from Microsoft that have to be applied to the target PC:
I have not had a chance to write code with VSTO, but considering that it was designed for such applications, I am assuming that you will not have most of the weirdness stated here. If you have Visual Studio 2005 Professional, then you can download VSTO here [3]. You can search on Microsoft's Download center for respective versions of VSTO for VS 2008 (for Microsoft Office 2003/2007).