From time to time, I have to work on environments which our customers provide and by the time we realize that they have forgotten to install a pre-requisite, its too late to ask them to mount back the dvd media or sometimes its just time sensitive.

After few searches online, I found this method which involves downloading a CAB file and installing it.

  1. Download microsoft-windows-netfx3-ondemand-package.cab
  2. Execute this on an elevated prompt
    DISM.EXE /Online /Add-Package /PackagePath:"D:\temp\Microsoft-Windows-NetFx3-OnDemand-Package.cab"

TIP: Alternative searches for the file if the link above breaks.
https://www.mmnt.ru/int/get?st=microsoft-windows-netfx3-ondemand-package.cab

Tada. No need for the DVD!

Reference: http://www.damirscorner.com/blog/posts/20170203-OfflineInstallationOfNet35InWindows10.html