.NET 11

.NET 11 is a Standard Term Support release with two years of support, while .NET 10 remains the supported long-term option. Its headline language change is C# 15 union types, which represent a value as one of a defined set of outcomes and let the compiler check that switch expressions handle every case. Closed class hierarchies provide similar checking for inheritance models. Other additions include collection-expression arguments, extension indexers, and labeled breaks and continues; memory-safety features remain in preview. F# 11 reduces compiler memory use and collection allocations. Developer tooling also aims to cut waiting: a Native AOT command-line host speeds up simple commands, and a persistent MSBuild server avoids repeated startup costs. The runtime includes hundreds of performance optimizations, expanded hardware support, and improved crash reports. Runtime Async, which can make live asynchronous call stacks clearer, remains an optional preview.

For application development, ASP.NET Core adds asynchronous validation, OpenAPI 3.2, and capabilities for Blazor and SignalR; experimental Blazor components support agent-driven experiences. Microsoft.Extensions.AI offers common abstractions for model access, while the Microsoft Agent Framework supports tool-using agents and coordinated workflows, including connections through MCP. The SDK includes an MCP server template. .NET MAUI makes CoreCLR its default runtime and improves XAML iteration and native controls. Library updates include Zstandard compression, simpler process execution, richer JSON support, and ways to adapt in-memory data to stream-based APIs. Additional tooling supports app inspection, testing, modernization planning, and mobile workflows. The release emphasizes productivity across web, cross-platform, and Windows development, with preview features and workload-dependent performance gains worth evaluating before adoption.