Which .netFramwork version do you need to install. The latest one (4.5.something or 4.6 preview) is already installed and an important part of Windows. See in the Windows Features if you can install 3.5 .netFramework (which is rather old now, normal 3.5 .netFramework programms work with 4.5 normaly) if you need this .netFramework version.
Been trying for hours to get NetFramework 3.5 to install on build 9901 with no luck, tried every single trick suggested from multiple Google searches but will not download. Using the above method I get the error below. Tried using both Windows 8.1 and Win10 9901 sources. Microsoft Windows [Version 10.0.9901] (c) 2015 Microsoft Corporation. All rights reserved. C:\WINDOWS\system32>dism /online /enable-feature /featurename:netfx3 Deployment Image Servicing and Management tool Version: 10.0.9901.0 Image Version: 10.0.9901.0 Error: 0x800f081f The source files could not be found. Use the "Source" option to specify the location of the files that are required t o restore the feature. For more information on specifying a source location, see hxxp://go.microsoft.com/fwlink/?LinkId=243077. The DISM log file can be found at C:\WINDOWS\Logs\DISM\dism.log C:\WINDOWS\system32>
Try mounting the 9901 dvd and running: Code: dism /online /enable-feature /featurename:netfx3 /all /limitaccess /source:X:\sources\sxs Make sure to replace the X with the actual letter of the mounted drive.
@SlimRock You can't install .NET Framework 3.5 on build 9901 using sxs folder from build 9600; the binaries are different.