Solved TargetFrameworkAttribute error with extension (wrong target framework)

I'm currently in the very early stages of making an extension for the Oxide Core which runs along side with the Rust extension. I can compile the code fine. The extension is loaded into the by Oxide without errors, its only when unity starts to initialise(i think) when i start getting errors.

The error:
Could not load type 'System.Runtime.Versioning.TargetFrameworkAttribute' from assembly 'Oxide.Ext.MyExt'.


My code:

The code is bare bones, but i just wanted to make sure it's working fine. I'm targeting with .net Framework 4.6.1. Could this be the error? Do i have to do specific initialisation for extensions?

Best wishes,
Sililia

 

This is for other with this problem especially Windows 8 and above Visual studio >2015, it doesn't show targeting for .net 3.5. By default, .net3.5 is disabled since Microsoft want to stop supporting it? https://support.microsoft.com/en-gb/lifecycle/search/548
To enable it, Search "Windows features", for me it was the first option, enable it. It will download through windows update; restart and you use .net 3.5 targeting on your IDE.


Hope it helped.

EDIT:
Thanks for the reply @Wulf

 

Just to clarify as I’m unsure if you’re contradicting what I was saying.
No matter how many times you install or reinstall the developer pack and or targeting pack for .net 3.5, if it’s disabled as a windows feature; visual studio will be unable to target it.