In my experience you will still "always" need .NET 2.0 or 3.5 (.NET Framework 3.5 feature set in Windows 8.x includes 3.0 and 2.0 also), so now I always install it righ away.
Most of the solutions on the internet tells you to grab the DVD/Mount ISO and point the 'dism.exe' to the SXS folder and enable it with the source files there. For a lot of us, those files aren't available when you need it, or not at all.
I just had this problem hit me again, as I just started a new consultancy assignment and got a new laptop from the work place I had to use. It came already installed with Windows 8.1 (over the network) and with all software and updates. Hence, enabling .NET Framework 3.5 (which wasn't enabled) I hit an error while installing from Windows Update: Error: 0x800F0906.
A long story short, here is what I did to actually make my computer enable .NET Framework 3.5 via Windows Update. The computer was also configured to use WSUS, but it was not locked down to deny me installing updates from Windows Updates (more/newer than those updates the IT department had approved). So if you are locked to only local WSUS this might not work. Or you can beg your IT department to enable this Group Policy (see below).
- Uninstall these three security updates (or those that was on my system):
- In Local Group Policy, I enabled 'Specify settings for optional component installation and component repair' under Computer Configuration > Administrative Templates > System. See illustration below.
Just to be sure settings were in effect, I rebooted. I could probably just force a gpupdate as well..
My next attempt to install .NET Framework 3.5 was suddenly a success!!