I'm not really sure what you're talking about then. What exactly is a .NET database? Every language has its own implementation of in-memory classes and instance

I'm not really sure what you're talking about then. What exactly is a .NET database? Every language has its own implementation of in-memory classes and instances, and these are translated over some protocol to a database that then translates to a on-disk format for persistence. That's how they all work, with various trade-offs. If you want a ".NET database", the only example would be to simply dump the in-memory bytes to disk, which you can through the various serializers in the framework.