Migrating and Upgrading Add-ins from Visual Studio 2005 to Visual Studio 2008
Add-ins created in prior versions of Visual Studio require changes before they will work correctly in Visual Studio 2008. You must either upgrade or migrate the add-ins. Upgrading add-ins refers to using a binary add-in file that was compiled in a prior version of Visual Studio in Visual Studio 2008. Migrating add-ins refers to updating and recompiling projects and code for use in Visual Studio 2008.
In the majority of cases, migrating add-ins is recommended to leverage the new Visual Studio functionality. Upgrading add-ins is an option for add-ins that do not use command bars and for users who do not need access to the new functionality. In Visual Studio .NET 2002 and Visual Studio .NET 2003, command bars were referenced in the Microsoft.Office component. This command-bar functionality is now available for Visual Studio in the Microsoft.VisualStudio.CommandBars assembly.
Visual Studio uses two methods for registering add-ins:
COM Registration — This method provides compatibility with add-ins created in versions of Visual Studio prior to Visual Studio 2005. The add-in is registered under the Visual Studio 2008 9.0 hive and as a COM class in the Windows registry. This is the method of registration used in Visual Studio versions prior to Visual Studio 2005.
XML Registration — This method uses an XML file to register add-ins with Visual Studio 2008.