How to create a version-independent COM add-in /
plug-in in Visual Studio .NET for Office 2007 -  2000

Your Office extensions are version-neutral

Unlike VSTO 2005 and 2008, Add-in Express core is specially designed to make your Office solutions version-independent. With Add-in Express you needn't create version-specific projects. You write your code once and have it work on all Office versions, from Office 2000 to Office 2007. Just include in your solutions version-neutral Office interop assemblies delivered with Add-in Express.

However, version-neutrality is not the only benefit you get with Add-in Express.

All your Office solutions are shared

Yes, all your Office solutions based on Add-in Express are shared. So, you can develop add-ins that work for all Office applications installed on your machine (see the picture above).

All pitfalls are bypassed

It is well known that each new release of Microsoft Office including its service packs has some minor bugs or troubles for Microsoft Office developers. Add-in Express is tested on all Microsoft Office versions and it gets around all known pitfalls that you might face when developing Microsoft Office plug-ins. So, be sure your add-in will work on all PCs of your customer.

Your solutions support all Microsoft Office suites, from Student to Enterprise

Unlike VSTO, Add-in Express supports all Microsoft Office suites, from Student and Home to Professional and Enterprise. With Add-in Express you increase the installation base for your Microsoft Office extensions.

Works on Visual Studio Express

Add-in Express .NET is developed in C# and directly supports Visual Basic® .NET (VB .NET), Visual C#, and Visual C++® in Visual Studio 2008, 2005 and 2003, as well as RemObjects Chrome. Besides, Add-in Express works on all editions of Visual Studio, so you can develop feature-rich extensions for Microsoft Office on free Microsoft Visual Studio 2005 and 2008 Express.