NETx Server products require the .NET Framework 3.5. The installation is typically done through an online installer during the setup process.

In some closed systems the internet connection is not possible. The NETx Server setup installer will fail on the prerequisite of .NET Framework 3.5.

This article guides you through the steps necessary to install the .NET Framework 3.5 in offline mode.

Installation can be done using the Windows installation media (DVD or disk image) of your Windows version (10, 11, Server 2016 or Server 2019).

If you do not have an installation media ready, you freely download it from Microsoft:

• Windows Server 2016: it is sufficient to use the evaluation version provided here: https://software-download.microsoft.com/download/pr/Windows_Server_2016_Datacenter_EVAL_en-us_14393_refresh.ISO
• Windows Server 2019: it is sufficient to use the evaluation version provided here: https://www.microsoft.com/en-US/evalcenter/evaluate-windows-server-2019
• Windows Server 2022: it is sufficient to use the evaluation version provided here: https://www.microsoft.com/en-US/evalcenter/evaluate-windows-server-2022
• Windows 10: use the media creation tool: https://go.microsoft.com/fwlink/?LinkId=691209
• Windows 11: use the media creation tool: https://go.microsoft.com/fwlink/?linkid=2156295  

Afterwards, do the following steps for installing .NET 3.5:

1. Insert the Windows installation disk in your CD/DVD drive so that Windows can access its content or mount the ISO disk image as a drive.

   1. For mounting an ISO image, right-click the ISO file and select "mount"

2. Open command prompt with administrative privileges

3. Issue the following command
   
   

   Dism /online /enable-feature /featurename:NetFx3 /All /Source:D:\Sources\sxs /LimitAccess

   and replace the source location according to the path of your Windows DVD.
   
   Installation will take a few minutes and result in a message that the operation completed successfully.

After that, re-run the NETx Server setup installer.

Troubleshooting

Following error codes are known to occur most commonly during the installation:

• 0x800F081F – The source files could not be found
• 0x800F0906 – The source files could not be downloaded

If you are connected to the internet and still are encountering this issue, this is because you have installed the following Windows updates:

KB2966826
KB2966827
KB2966828
These are the security updates for .NET Framework 3.5 which must be installed on the current installation of the framework. But since Microsoft applies these updates regardless of whether framework 3.5 is installed or not, they get installed even when the framework is not installed.

If these updates are installed first and then you try to install the framework, you will get the above mentioned errors. You will need to uninstall the above mentioned updates, install the .NET Framework 3.5 through one of the methods mentioned above and finally install the updates again.

Article applies to the following products:

• NETx BMS Platform
• NETx Multi Protocol Server
• NETx BMS Server 2.0