With .NET's annual major release cadence, we get a new set of language features at our fingertips every November.

The latest version of the C# compiler — C# 15 — brings us
// Collection Expression Arguments, an addition to C# 12's Collection Expressions
// Union Types and Patterns, at long last
// Closed Class Hierarchies, the foundation of Unions for exhaustive matching
// Extension Indexers, improving Extension Members introduced in C# 14
// Unsafe Evolution, a preview feature that catches up with two and a half decades of updates to .NET
// Runtime Async, replacing the compiler-generated async state machines yielding better performance
among other features.

Additionally, in this live coding session, we will also review breaking changes, as well as related improvements in the .NET 11 SDK and runtime.

Let's code some C# 15!