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Saving C# 15 unions with System.Text.Json in .NET 11

Part 4 of NimblePros' domain modeling series walks through saving C# 15 unions and closed hierarchies with System.Text.Json on the .NET 11 RC1 SDK. It shows where the built-in classifiers are enough and where a hand-made "kind" discriminator is still needed. Useful for any developer persisting polymorphic domain state to JSON.

Why stable instruction addresses beat numeric indexes in a C# compiler

The author of the C# interpreter HydraScript explains why numeric instruction indexes broke code generation and how switching to stable IAddress objects fixed it. Addresses now stay with their instructions when code is inserted, removed or replaced, so jumps keep pointing to the right place. It is a concrete case for developers building compilers or interpreters with the Visitor pattern.

What's new in C# 15: unions, closed hierarchies and more

An overview of the C# 15 features: union types, closed class hierarchies, named break and continue, extension indexers, with-arguments in collection expressions and the revised unsafe model. It shows how each one changes everyday code and where the caveats are.

Closed hierarchies in C# 15: exhaustive pattern matching for class types

C# 15 adds the closed modifier, which limits derived types of a base class to the same assembly. The compiler then knows the full list of subtypes and can flag switch expressions that miss a case. This helps .NET developers catch new cases at build time instead of finding silent runtime bugs in game logic or domain rules.

C# 14 Extension Members: Extension Properties, Static Members and Operators

C# 14, shipped with .NET 10, adds extension members: extension properties, static members and operators declared inside extension blocks. This goes beyond the classic this-parameter extension methods and lets APIs read more naturally. Knowing the current limits, such as no state and no indexers, matters before adopting it in production.