Microsoft has released .NET 11, a Standard Term Support version that brings C# 15 language additions, ASP.NET Core updates, and runtime and SDK performance work.
The release adds improvements across C# 15, ASP.NET Core, .NET MAUI, and Windows development, along with hundreds of runtime optimizations and a more responsive SDK. .NET 11 is a Standard Term Support release with two years of support, while .NET 10 remains available as a Long Term Support option. Microsoft also invites developers to .NET Conf, held November 10 to 13, 2026.
C# 15 introduces union types, which let a value be one of a declared set of case types, with compiler-checked switch expressions that flag unhandled cases. Closed hierarchies limit direct derivation to the declaring assembly, giving the compiler what it needs to check patterns over those types. Smaller additions include collection expression arguments, extension indexers, and labeled break and continue statements.
On the tooling side, the SDK enables a Native AOT CLI host by default, so commands like help and version queries can run faster, and the MSBuild server stays warm between invocations. Runtime Async, still a preview feature, moves asynchronous suspension into the runtime and gives profilers and debuggers clearer call stacks. The libraries add Zstandard compression, a FullJoin operator for LINQ, and new in-memory stream adapters that avoid copying data first.
Source: .NET Blog
