Installing .NET Framework 3.5 on Windows 10 through Control Panel, Turn Windows Features On or Off might result in Error code: 0x800F081F. This might just be for computers that use WSUS with an Intranet location specified. I have not been able to test with a Windows 10 computer not using WSUS that didn’t already have .NET 3.5 installed.
The usual work around for installing .NET on the Windows Server OS is a registry key telling it to bypass WSUS and get the needed files from Windows Updates. That fix, with the RepairContentServerSource Registry entry, does not solve the problem when trying to install .NET 3.5 on Windows 10. Nothing changed with or without the key present.
To get the .NET Framework 3.5 installed on Windows 10, this is the method that I found to work consistently.
- Insert your install media or mount the ISO for your Windows 10 version. Note the drive letter.
- Open an elevated Command Prompt (Run as Administrator)
- Enter the command: dism /online /enable-feature /featurename:Netfx3 /Source:E:Sourcessxs
(replace ‘E’ with the proper drive letter for the source of your installer)
- Press enter and the process should progress through completion.
After rebooting, the .NET Framework 3.5 (includes .NET 2.0 and 3.0) will be available on the computer. If you head to the Turn Windows features on or off dialog, you will notice that the top .NET Framework 3.5 option is now checked.