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Union types in C# | DEM304

Microsoft Developer (Build) · Jun 03, 2026 · Engineering Insights

C# 15, shipping November, adds its own 'Goldilocks' version of union types to the language.

“we're just going to show you how unions should be.”

C# lead designer Matt Torus and engineer Dustin Campbell demoed union (discriminated union) types coming to C# 15 in November, already available in preview. This is a general programming language feature with no meaningful AI industry signal, relevant mainly to .NET developers rather than AI conference intelligence.

csharp language-features union-types microsoft-build dotnet

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