.NET 11 ships with C# 15, union types and closed hierarchies
The annual release is a two-year Standard Term Support version, landing closed hierarchies, extension indexers, and experimental EF Core vector search alongside the new language features.
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From The Wire
.NET 8 and .NET 9 reach end of support today
Microsoft stops shipping security patches for both versions from 10 November 2026, with .NET 10 as the only supported upgrade path.