The new Roslyn incremental generator API is pretty good these days but not well documented yet. I’ve been using it with json-schema to save a lot of boilerplate and provide a more intuitive declarative framework in a large side project.

I have an older variant on this hacked together as a weekend project.

https://github.com/CharlieDigital/js2c

Takes an input snippet of JSON and builds up classes as serialization targets.