How can Visual Studio Code on OSX import sln/csproj and run?
Visual Studio Code isn't designed to work with sln/csproj files unfortunately (or fortunately depending on how you look at it).
In order to use your project created in Windows create a .NET Core application and use 'Portable Class Libraries' instead of standard class libraries then Open Folder in Visual Studio Code.
You can open it, using vscode-solution-explorer link for more info
(P.s. Not everything works as smoothly as we would like, but it's still better than nothing)