Microsoft released .NET 11 on November 10, bringing C# 15, changes to ASP.NET Core and Entity Framework, and a new default runtime for .NET MAUI applications. The Standard Term Support release receives two years of updates. Microsoft release announcement
C# 15 adds union types and closed hierarchies
Union types let developers declare a result with a fixed set of possible case types. For example, a product lookup might return either a Product or a ProductNotFound value. The compiler checks switch expressions for coverage of those cases, helping catch missing handling as the application evolves.
Closed hierarchies address a related problem. A closed class restricts direct inheritance to its declaring assembly, giving the compiler enough information to check patterns across the hierarchy. C# 15 also adds extension indexers, labeled break and continue statements, and constructor arguments inside collection expressions. The language becomes the default for projects targeting .NET 11. C# 15 documentation
ASP.NET Core adopts OpenAPI 3.2
ASP.NET Core now generates OpenAPI 3.2 documents by default, including descriptions of individual events in server-sent event streams. Teams using older client generators can still select an earlier document version.
Asynchronous validation lets rules await database queries or remote services. Minimal APIs and Blazor forms support the new asynchronous DataAnnotations APIs. SignalR adds authentication refresh during an existing connection, allowing applications to update a user's identity without reconnecting.
Blazor adds CacheView for caching rendered component subtrees during static server rendering. Interactive Server applications also gain an optional mechanism to pause inactive browser circuits and release their server resources. Enabling circuit pause requires an additional package and configuration. ASP.NET Core release notes
The CLI starts through Native AOT
The SDK enables a Native AOT command-line host by default. Help, version queries, and supported commands run through the native path. Commands requiring managed execution fall back to the managed CLI. A persistent MSBuild worker reduces repeated startup work across build and test commands.
Container publishing gains reproducible image digests through SOURCE_DATE_EPOCH. NuGet source configuration adds a minimum package publication age, giving teams control over how soon newly published dependencies become eligible for selection. SDK and tooling changes
Elsewhere in the release, the libraries add Zstandard compression, JSON Lines output, and a LINQ FullJoin operator. Entity Framework Core improves query translation and requires .NET 11. Microsoft also includes an MCP server template for exposing application tools to AI clients. Runtime Async and the Blazor AI components retain preview or experimental status. Library and framework changes
.NET MAUI adopts CoreCLR across its supported platforms. On Apple platforms with restrictions on runtime code generation, CoreCLR uses precompiled code and an interpreter. Native AOT remains an optional publishing approach, with Android support still experimental. MAUI runtime changes
The launch coincides with the November 10 support cutoff for .NET 8 and .NET 9. .NET 10 LTS remains supported through November 14, 2028. Existing applications need compatible target frameworks, packages, workloads, and deployment runtimes when moving to .NET 11. Microsoft support policy
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