Documenting the code is part of the Software Development Life Cycle. There are many ways to document APIs. Visual Studio XML comments provide an option to document the code (Modules, Class, Interfaces, and Methods) in-line. These comments can be extracted from the code to generate a HTML(.chm) file.
Below are some of the Documenter tools
·Sandcastle– This tool provides high customization but does not have GUI capabilities. Sandcastle can be used along with Sandcastle Help File Builder to have a power of GUI. This is highly recommended as this is supported by Microsoft.
Download Link:
Sandcastle: http://www.codeplex.com/Sandcastle
Sandcastle Help File Builder: http://www.codeplex.com/SHFB
· Doxygen- This is yet another tool for document builder.
MoreInfo:
http://www.stack.nl/~dimitri/doxygen/
·NDoc: This tool is “obsolete”. As they have not updated the tool long time.
Preps Blog 