The .NET Documentation will also need to be downloaded if you plan to utilize offline - Help Viewer dialog, Manage Content tab, 'Online' Installation source, but now go through the list of available content, such as .NET Framework #.#, Visual Studio 2015: Visual Basic and Visual C#, etc. selecting 'Add', and then perform another 'Update'.
As for how to integrate AutoCAD Help Online - I have no idea (never tried)?
I'll see what I can find out, the next chance I get between projects.
Ciao