[codedokode]

You can emulate sum types with classes and inheritance (N classes inherit from an empty base class), can't you?

[bestouff]

It's very clunky

[mastry]

Yes, very clunky. One of the big issues with this approach is that switch expressions still require a default branch because there’s no way in C# to express a completely closed set. This makes future changes to the set (sum type) hazardous.

They continue to fiddle with design approaches to solve this. See https://github.com/dotnet/csharplang/blob/main/meetings/2025...