I’ve been …. how to say …. “annoyed” to be able to install the .net framework 3.5 on my Windows 10 development system. This is a prerequisite for installing WixToolset (excellent program for generating installation files).

Going through the addition of functionality, I ran into the error 0x800f081f that I choose (or not), recover files on Windows update. Ditto trying to install it from the runtime binaries available at MS.

After having read the useless article of the technet concerning this error, I finally found the solution:

• Start a PowerShell session “as administrator” (clic on the french capture below)

• Connect the installation media (CD or iso) of your windows 10
• Type in the PowerShell window:
  DISM /Online /Enable-Feature /FeatureName:NetFx3 /All /LimitAccess /Source:<YOUR_CD_DRIVE>:\sources\sxs
• Force a system update by launching Windows Update

NB: <YOUR_CD_DRIVE> is the drive letter containing Windows 10 sources