What's the coolest thing coming in the next version of C#?
C# 15 will add union types, shipping November with preview available now
“It's like it's either a cow, a sheep, or a pig, and then uh use that type uh in a strongly typed fashion.”
C# 15 will introduce union types, allowing developers to express a closed set of unrelated types in a strongly typed way with full switch exhaustiveness checking. The feature ships in November 2026 with a preview already available in Visual Studio and VS Code. This is a language feature announcement with no meaningful AI industry signal.