1. Shouldn't obsolete SDK versions be removed?
2. This PR isn't suitable to be merged before the actual compilation/debugging support for .NET 7/8 is added.

The problem is also when compiling. Dotdevelop uses mono msbuild fork (really outated) instead of real msbuild to compile net core projects. Because mono msbuild can compile some versions of net core and mono framework projects. Instead of dotnet msbuild which have removed support for compiling mono.

See:

dotnet/msbuild#8528

And also to remove mono msbuild is not a solution, because than we cant built mono/classic .net framework related projects. So an option would be to support both build engines and build all net core projects every time with real msbuild and mono/classic net framework related things with mono msbuild.

And the next thing is dotdevelop uses a build path for finding msbuild and new msbuild seems to do not have that path. You can simple run a terminal and dotnet msbuild, I think so.

https://github.com/Aptivi-Archives/msbuild-offline-packaging

There was an interesting project to update mono msbuild to version 17.

But there is also an open PR from there, wich never got merged into offical msbuild.

mono/msbuild#435

Not tested yet, but maybe it is useful?

@MakiWolf Technically you can have your own MSBuild distribution (JetBrains proves the possibility and limitations, in https://blog.jetbrains.com/dotnet/2018/04/13/introducing-jetbrains-redistributable-msbuild/), but if you want to do that for this small initiative the ROI can be low.