Rebuild VSTO-O add-in on .NET2.0 RC1

Last week our VSTO-O add-in would not load when installed on new client PCs. This was caused by the automatic download and installment of .NET2.0 RC1 performed by the VSTO setup project, while the add-in was built with .NET2.0 beta 2. A rebuild of the add-in and the setup project was needed to make things work. Thus, I had to uninstall all beta 2 stuff, including .NET, Visual Studio 2005, VSTO runtime, SQL Express, etc. After that, I installed VS2005 RC1 on my PC, which now includes the VSTO project templates by default.

The existing VSTO-O project compiled without problems in VS2005 RC1, so I didn't need to create a new project and move the code manually as I had to when going from VSTO alpha to VSTO beta. You might not be that lucky (see the article referenced below).

Some modifications was needed for the setup project. In beta 2, you had to manually add several VSTO assemblies (DLLs) and install them to your target folder. I removed all those VSTO assemblies, and did a 'refresh dependencies', which in RC1 is able to correctly detect and add the required VSTO assemblies to the setup kit.

The add-in would, however, still not load in Outlook. As I know the details on how to get a VSTO-O add-in to load, I quickly turned to the registry to check the CLSID InprocServer32 setting for my add-in. In VSTO-O beta 2, the add-in loader was named VSTAddin.DLL, while it in RC1 has got the documented, correct name AddinLoader.DLL. Use 'View-Registry' in the VS2005 setup project, navigate to HKCU\Software\Classes\CLSID\{guid}\InprocServer32\ key and change the name of the VSTO loader stored in the (default) setting.

With these changes to my setup project, the add-in now installs, loads and works correctly on RC1.

Note that modifying the setup project is not needed if you choose to start with a new VSTO-O project and move the code manually from the old beta 2 project.

Mads Nissen has posted an article that describes how to get your VSTO-O add-in to work with .NET2.0 RC1 and details about making a fully automated setup kit using a custom prerequisite with the setup project. He has also updated the CAS custom installer action to support uninstall.