Enable .NET Framework 3.5 by using Windows PowerShell
For a Windows Server installation that is not connected to the Internet, you can use Windows PowerShell to add .NET Framework 3.5 and provide access to the \sources\sxs folder on the installation media. The \sources\sxs folder can be copied to network share (for example, \\network\share\sxs) to make it easily accessible to multiple computers. The target computer account DOMAIN\SERVERNAME$ must have at least read access to the network share.
Windows Server 2012 or Windows Server 2016
Administrator user rights. The current user must be a member of the local Administrators group to add or remove Windows features.
Target Computers might need network access and rights to use either alternate sources or an Internet connection to use Windows Update.
Start Windows PowerShell in the Administrator Command Prompt by typing:
To install .NET Framework 3.5 from installation media located on a network share, use the following command:
Install-WindowsFeature Net-Framework-Core -source \\network\share\sxs
Where \\network\share\sxs is the location of the source files.
For more information about the Install-WindowsFeature cmdlet, see Install-WindowsFeature.
To verify installation, run the following command:
The Install State column should show Installed for the .NET Framework 3.5 (includes .NET 2.0 and 3.0) feature.