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:
• Microsoft .NET Framework (I personally installed 2.0 though latest versions should also work)
• KB 908002 (http://support.microsoft.com/kb/908002) - Download and execute the EXE file. The EXE download actually contains 3 files all of which has to be applied to the target system in the following order:
1. lockbackRegKey.msi
2. office2003-kb907417sfxcab-ENU.exe
   
3. extensibilityMSM.msi
• Office 2003 Primary Interop Assemblies (http://www.microsoft.com/downloads/details.aspx?FamilyId=3C9A983A-AC14-4125-8BA0-D36D67E0F4AD&displaylang=en) - The download (an EXE file) contains an MSI file that has to be run on target system.
  
  As far as I can tell KB 908002 and the Office 2003 Primary Interop Assemblies cannot be uninstalled.
  

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).

Acknowledgements:

1. http://social.msdn.microsoft.com/forums/en-US/vsto/thread/10c10162-4841-4b46-9d54-67adfecbf622/
2. http://msdn.microsoft.com/en-us/library/kh3965hw(VS.80).aspx
3. http://www.microsoft.com/downloads/details.aspx?FamilyID=8315654b-a5ae-4108-b7fc-186402563f2b&DisplayLang=en