.NET framework 3.5 source files could not be found

If you are having trouble installing previous versions of the .NET framework on Windows Server 2012 and above, or are receiving the following error listed below, use this set of instructions.

Installation failing

Find and mount the original Windows Server 2012 ISO.  An important thing to make note of is the drive letter that the image gets mounted as.

Mount the ISO

Once the ISO is mounted and we have correctly identified the drive path we need to enable the .NET Framework.  This can be done through command line using the dism.exe command or alternatively throught the Windows GUI.

First we need to enable the .NET features on the server.  Notice in the command I am using the F: drive.

dism.exe /online /enable-feature /featurename:NetFX3ServerFeatures /Source:F:\sources\sxs

Next, to enable the specific .NET framework we want just use the following command:

dism.exe /online /enable-feature /featurename:NetFX3 /Source:F:\sources\sxs /LimitAccess

Successful completion of this command should look similar to the output below.

enable .net

Using the GUI the instructions are similar and pretty straightforward.

  1. Insert Windows Server 2012 DVD or ISO.
  2. Open Add Roles and Features Wizard.
  3. Select .NET Framework 3.5 Features and then click next.
  4. Select “Specify an alternate source path link in the Confirm installation selections screen”.
  5. Path: F:\Sources\SxS and then click OK.
  6. Click the Install button.

That should be it.  Definitely an easy fix but not very obvious.

Josh Reichardt

Josh is the creator of this blog, a system administrator and a contributor to other technology communities such as /r/sysadmin and Ops School. You can also find him on Twitter and Facebook.