I download the compiled help files (CHM) for .Net Runtime v100.0. In Windows 10 the contents display but none of the detail appears. Probably everyone knows this but it's not mentioned in this forum. Right click the file, choose properties, and unblock. Then the details appear.
Come on ESRI! Maybe you could provide the off-line help as HTML?
We really appreciate your feedback and will add this tip to the Guide documentation (online and offline). The change was introduced in Windows a while back to reduce security vulnerabilities in HTML Help.
CHMs are still seen as a great portable format for delivering offline documentation but we're always considering and researching alternatives, such as MS Help Viewer 2.X or a full local copy of the .NET Developers site content.