When programming in Microsoft Office Word 2007, the tools and techniques needed to program using C# for applications are VSTO 3.0, Visual Studio 2008, and the .NET framework. So far, we've learned that by using VSTO 3.0, we can program forms, controls, objects, and error handling, and have learned that VSTO 3.0 enables rapid application development for Microsoft Office solutions. VSTO 3.0 gives the Office developers the flexibility to create document-level customizations and application-level add-ins by using Visual C#, .NET, and Visual Studio 2008.
Microsoft has come up with a variety of Word 2007- supported objects that are exposed from the Office object model, allowing Office developers to program against the exposed objects for the development and customization of Word 2007. In general, while automating the Office applications using managed code, you program against the primary interop Office assemblies.