How to fix Error Code 0x800F081F when .NET Framework 3.5

Another day another problem minor or major. Today while debugging a new application, I got an exception for missing .Net Framework 3.5 service pack 1.
It was a surprise for me as I was working on Windows 10 machine. When I opened registry editor(regedit) and reached the location
(HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP) I saw I only had .Net Framework 4 and above.
It was an easy fix, my initial thought but it was not.

At first I downloaded the .net framework from Microsoft( https://www.microsoft.com/en-us/download/details.aspx?id=21). When I tried to install I got below error.
.NET Framework 3.5 installation error: 0x800F081F

Error_0x800F081F

Then I tried installing the .NET 3.5 Framework using “Turn Windows features on or off” from “Programs and Features” window. (Steps below)

a) Press “Windows Logo” + “R” keys on the keyboard.
b) Type “appwiz.cpl” in the “Run” command box and press “ENTER”.
c) In the “Programs and Features” window, click on the link “Turn Windows features on or off”.
d) Check if the “.NET Framework 3.5 (includes .NET 2.0 and 3.0)” option is available in it.
e) If yes, then enable it and then click on “OK”.
f) Follow the on-screen instructions to complete the installation and restart the computer, if prompted.

This should have installed the .NET Framework 3.5 feature on the computer but unfortunately it didn’t work for me. I still got the same error.

After browsing many pages and articles I figured out the problem was with registery key UseWUServer(UseWindowsUpdateServer). Registry key UseWUServer was set to “1”.

regedit

I needed to set its value to “0” then it will ignore the intranet server and go to synchronize with Microsoft Update.

After setting UseWUServer value to “0”, I tried installing .NET Framework with above steps and it worked for me.

Hope this might help someone else in the future if they run into the same problem.

 

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