[Solved] Where I can find proper guidance to create Add-in for Revit using C#? [closed]

Your first port of call should definitely be the official Revit Developer Centre:

http://www.autodesk.com/developrevit

Work through the DevTV and My First Revit Plugin tutorials. That will provide all you need.

The Building Coder provides a comprehensive overview of the Revit API getting started material for self-learning:

http://thebuildingcoder.typepad.com/blog/about-the-author.html#2