Upgrade a .NET Framework 4.8 plugin to .NET Core in Visual Studio?

[ale2x72 (Alessio Erioli)]

Is there a way to actually upgrade a Grasshopper plugin built upon a .NET Framework 4.8 Visual Studio template to use also .NET Core?

So far, I’ve read the following guides and threads:

Moving to .NET Core

Upgrading VS 2022 solution from Rhino 7 to Rhino 8 SDK

My plugin seems to build and run properly now in Rhino 8, but when exiting Rhino 8 while at debug mode I get the following exception: [image] Is there something missed when configuring the Rhino 8 upgrade?

Time to test your plugins with Rhino 8!

Hi Rhino Developers, it’s time to test your plugins with Rhino 8 if you haven’t already! In particular, the move to .NET 7 is an enormous change which might trip up some existing plugins, which means some plugins might need a few tweaks to work. The benefit can be huge, .NET 7 provides much better performance in a lot of scenarios and we’re now using the exact same runtime on both Windows and Mac. We’ve collated some important information that you might need to know regarding Rhino 8 and the …

Moving plugin to Rhino 8

Hey @samlochner, If you want to support Rhino 7 (win and/or mac), you’ll need to release net48 until you sunset that support. Also to keep in mind. Rhino 8 will likely run net48 for its lifetime as Rhino 8 still runs net48, and Rhino.Inside.Revit is quite popular and has to use the same framework. In theory, for now, supporting just net48 is easier (if you don’t want to do Mac). You can of course start multi-targeting now so you’re prepared for the switch to dotnet and or cross-platform. You’…

All of them suggest a new project using the updated template, either as a starting point or as an added launcher for debugging in Rhino 8 (which I’ve done, but that’s not what I want). I’ve not yet seen a way of actually upgrading a .NET Framework 4.8 project to use also .NET Core. I’m talking about a project whose properties in Visual Studio still look like this:

If I click on “Install other frameworks…” I just get redirected to this site, but nothing changes even after installing the SDK libraries. Of course, .NETCore SDK libraries are already installed on my PC (both 7.0 and 8.0).
I’ve tried to use multiple <TargetFrameworks> in the .csproj file as CSykes suggests here: in my .csproj file there is a <TargetFrameworkVersion>v4.8</TargetFrameworkVersion> line, and if I try to replace it with <TargetFrameworks>net4.8;net8.0<TargetFrameworks> I get an error code 0x80004002 in the solution, and the solution itself is not loaded.

So, is there an actual way to upgrade an old 4.8 project to use also .NET Core? Or is starting from a new, updated template the only way? If so, how can I preserve the old plugin GUID so that it is effectively a new version and the new version does not install in parallel with the old one? Or maybe I just missed something along the way?