While we enter the comments in xml, of a project. Do not think those are only useful for developer who is developing the site. Those are also useful when we need to create helpfile.
To Create help file from those xml comments, we may use a software "Sandcastle". This software is provided by Microsoft. Official download link is "http://shfb.codeplex.com"
After install this software, We need to create a project and add .dll file in Resource. Now Build that. It will take time vary from .dll file. After creating a help file it will show a line with path of help file in process screen. It will create .chm page.