C# 15 ships with .NET 11. It adds union types, closed hierarchies, a preview of the updated unsafe model, and a few smaller changes that remove everyday ceremony.
Route requests across models and providers natively in Microsoft.Extensions.AI with RoutingChatClient, SemanticRoutingChatClient, and FailoverChatClient — new experimental primitives for content-based routing, failover, and custom routing policies.
Find out about the new features in .NET 11 Preview 7 across libraries, runtime, SDK, C#, ASP.NET Core, .NET MAUI, Entity Framework Core, F#, and Windows Forms.
Microsoft.Testing.Platform brings failures into GitHub Actions and Azure DevOps, uses pipeline history to separate regressions from flakes, and preserves usable reports when a test host crashes.
MCP C# SDK v2.0 implements the 2026-07-28 specification with a stateless-first protocol, standardized HTTP headers, and Multi Round-Trip Requests for interactive tools, all while staying backward compatible.
Find out about the new features in .NET 11 Preview 6 across runtime, SDK, libraries, ASP.NET Core, .NET MAUI, C#, Entity Framework Core, F#, and container images.