"omnisharp.enableImportCompletion": true,
"omnisharp.enableRoslynAnalyzers": true,
"omnisharp.organizeImportsOnFormat": true,
Then https://github.com/nx-dotnet/nx-dotnet. Use NX to manage the mono repo and the .net (and other languages) of projects.
Can then pnpm nx run-many --target=build --all
to build all projects, .net or otherwise.