Downgrading .NET 4.8 on Windows Server 2012 R2

Published by John on July 2, 2020 Under Sysadmin

Recently, while setting up a server running Windows Server 2012 R2, I ran into some issues installing the vendors software. The vendor provided a tool for checking the system to make sure the specs, like number of cores, memory, hard drive space, and installed software is correct.

The Server, which is a beefy 2 Xeon processor, with 48 cores and 64 GB memory passed all the tests, but failed when checking the .NET version. The tool was looking for .NET version 4.5, but the server had .NET 4.8.03761 installed.

Normally, that wouldn’t be an issue, as Microsoft intends each release of .NET, at least in the same major version, to be backwards compatible. However, the vendor’s software tool would not continue with that version.

After a bit of reading, I determined that on Windows Server .NET are installed as updates using Windows Update, so to downgrade, you need to know the correct update name, like KBXXXX. Unfortunately, there isn’t an easy way of finding this just within windows update, the control panel, or otherwise. However, after a bit of searching, I determined that for Windows Server 2012 R2, .NET 4.8 is installed with this update: KB40545664

To downgrade .NET, I opened control panel, clicked on view updates, searched for KB40545664, and uninstalled it. After rebooting the server, it showed version 4.5 when I viewed the Registry Key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full

At a Glance: The Fix

To downgrade from .NET 4.8, uninstall update KB40545664 and restart server.

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