.NET 11 Released with C# 15, AI Enhancements, and Performance Gains

Summary of the .NET 11 Release

Microsoft announced the release of .NET 11 on November 10, 2026, bringing new features across languages, runtime, AI tooling, and developer productivity. This standard-term-supported (STS) update focuses on modern application development, including C# 15 with union types, native ahead-of-time (AOT) compilation improvements, enhanced AI libraries, and hundreds of runtime optimizations.

Who Should Care?

Software developers building applications using .NET, especially those invested in C#, ASP.NET Core, .NET MAUI, and AI integration, should be particularly interested. This includes developers working on web, mobile, desktop, and AI-enabled applications who want to leverage the latest language features, runtime efficiencies, and improved productivity tools.

Key Features and Improvements

• C# 15: Introduces union types for expressing distinct sets of possible values with compiler-checked pattern matching, plus closed class hierarchies to restrict inheritance and aid exhaustive pattern checks.
• SDK and Tooling: The SDK ships with a native AOT CLI host and a warm MSBuild server for faster command execution. Developers can also create and manage solution filters and benefit from enhanced ‘dotnet watch’ features.
• Runtime and Performance: Hundreds of optimizations including JIT compiler enhancements, reduced bounds checks, shared interface dispatch helpers, and improved hardware instruction support. New in-process crash reporting is now available on Linux and macOS.
• AI and Agentic Development: Includes Microsoft.Extensions.AI for model abstraction, a new MCP server template for AI tool integration, and Microsoft Agent Framework to build agentic workflows. Experimental Blazor AI components enable advanced AI interfaces.
• .NET MAUI: Gains CoreCLR as the default runtime, alongside better XAML iteration and native control support.
• Libraries: New Zstandard compression support, enhanced process execution APIs, expanded JSON and LINQ capabilities including JSON Lines and FullJoin, plus improvements in cryptography and DNS resolution.
• Entity Framework Core 11: Improved query translation reducing unnecessary joins and enabling more LINQ queries to be expressed natively in SQL.

Next Steps for Developers

Developers should:

1. Upgrade projects targeting .NET 11 to take advantage of new language features like union types and closed hierarchies.
2. Explore the new AI libraries and frameworks to integrate AI-powered capabilities into applications.
3. Benchmark applications to evaluate performance improvements and validate behavior, especially when adopting runtime async features that are still in preview.
4. Leverage the native AOT CLI host and improved SDK tooling to speed up development workflows.
5. Review EF Core 11 changes to optimize LINQ queries and SQL generation.
6. Monitor support timelines since .NET 11 is STS with two years of official support; consider continuing with .NET 10 LTS if longer support is needed.

Summary Checklist

• Update to C# 15 for new language capabilities.
• Test Runtime Async preview before full adoption.
• Use new AI SDKs for agentic and model-driven development.
• Evaluate performance gains with runtime optimizations.
• Upgrade EF Core models and queries accordingly.
• Adopt enhanced SDK tooling for developer productivity.