Microsoft releases .NET 11 with C# 15, AI and AOT updates

Microsoft has released .NET 11 with updates to its programming languages, runtime, development tools, and application frameworks. C# 15 introduces union types and closed hierarchies to improve how developers handle different application states, while SDK and runtime improvements help reduce startup times and improve performance. The update also includes new debugging capabilities through Runtime Async, which remains in preview.

AI development is another focus of .NET 11, with a built-in Model Context Protocol (MCP) server template and tools for building AI applications and agents through Microsoft.Extensions.AI and Microsoft Agent Framework. For web development, ASP.NET Core 11 adds asynchronous validation, OpenAPI 3.2 support, and improvements to SignalR. Blazor also introduces better caching, reduced resource usage for inactive connections, and experimental AI components for chat and agent interactions.

For mobile and desktop development, .NET MAUI now uses CoreCLR as its default runtime and adds improvements to XAML Hot Reload. Entity Framework Core 11 also improves database queries and JSON support, with experimental vector search capabilities for SQL Server. Microsoft has also confirmed that .NET 8 and .NET 9 reached end of support on November 10, leaving .NET 10 as the longer-supported LTS alternative to .NET 11.