Manually change Framework in runtimeconfig.json?

Hi, I’m working on upgrading our legacy Windows app to .NET 5.

In our legacy architecture, we used to have WinForms and WPF in many assemblies. At the same time, we had a headless version of our app that was running the same assemblies but detouring the UI code in runtime. That worked well on Linux under Mono.

In .NET 5, I see that as soon as I enable WPF and/or WinForms for the project, its target Framework changes to Microsoft.WindowsDesktop.App. With this, the app cannot be run on Linux.

However, if I manually change the Framework in runtimeconfig.json to Microsoft.NETCore.App, the app loads and our detour code seems to work as it did before.

I wonder if there’s an official/supported way to implement this scenario?

Thanks!

[Alovchin91]

@sfoslund Hi, sorry for the late reply. Yes, I’d say we’ve found a workaround. We have to manually patch runtimeconfig.json and deps.json to include dependency on mocked System.Windows.Forms.dll, but that should work for us for now.

Please feel free to close this issue. I’ll reopen it shall I need further assistance 🙂 Thank you!

[AraHaan]

What if you needed to manually have the project use the runtimeconfig.json file manually created because the SDK incorrectly list the wrong framework last which is a problem because that runtimeconfig.json is itself part of another framework which then gets used in a project which results in the the host (fxr) to incorrectly look for hostpolicy in the wrong framework? I tried to work around it myself by adding the NETCore.App framework last manually to no success as the runtimeconfig.json file still generates with it listed first instead of last.