The Revit .NET API allows you to program with any .NET compliant language including Visual Basic.NET, C#, and C++/CLI.
Revit Architecture 2012, Revit Structure 2012, and Revit MEP 2012 all contain the Revit Platform API so that you can integrate your applications into Revit. The three APIs are very similar and are jointly referred to as the Revit Platform API. Before using the API, learn to use Revit and its features so that you can better understand the relevant areas related to your programming. Learning Revit can help you:
Maintain consistency with the Revit UI and commands.
Design your add-in application seamlessly.
Master API classes and class members efficiently and effectively.
If you are not familiar with Revit or BIM, learn more in the Revit product center at www.autodesk.com/revit.