Last week, Microsoft released the second preview of .NET 11, bringing a wide range of improvements across its development platform. As reported, the release covers updates to the runtime, SDK, libraries, ASP.NET Core, Blazor, .NET MAUI, F#, and more. The preview is available now, and as stated, it represents a significant step forward in the platform's ongoing development cycle.
ASP.NET Core gains native OpenTelemetry tracing support in this release. The framework now adds OpenTelemetry semantic attributes directly to HTTP server activity, meaning developers no longer need the separate instrumentation library to collect standard tracing data. Attributes such as request method, URL path, response status code, and server address are now populated automatically by the framework itself.
Blazor Server-Side Rendering now supports TempData, allowing data to persist across HTTP requests, which is useful for flash messages, redirect flows, and one-time notifications. The feature is registered automatically and uses ASP.NET Core Data Protection for encryption by default.
A new dotnet new webworker project template has also been introduced, allowing Blazor WebAssembly applications to offload heavy computations to a Web Worker without blocking the UI thread, keeping applications responsive during demanding operations.
Kestrel's HTTP/1.1 request parser has been reworked to avoid throwing exceptions on malformed requests. As stated, throughput improvements of 20 to 40 percent have been reported in high invalid-traffic scenarios such as port scanning or misconfigured clients.
The Map control in .NET MAUI has received significant attention in this preview. Developers can now define map coordinates directly in XAML using a simplified syntax, removing the need for verbose markup that was previously required. A new Map.Region bindable property also allows developers to set the map's initial region declaratively.
Map elements such as polygons, polylines, and circles now support visibility toggling and draw-order control through new IsVisible and ZIndex properties, enabling more dynamic and interactive map overlays. Click events on the map elements are also now supported on both Android and iOS, opening the door for richer user interaction without additional workarounds.
Binding performance has also improved considerably in .NET MAUI. TypedBinding and SourceGeneratedBinding are reported to be approximately 29 percent faster with 50 percent less memory allocation per operation, thanks to delegate caching, binding mode caching, and the removal of unnecessary type conversions. As described, the long-standing bug affecting empty-string binding to nullable value types has been resolved, correctly setting the bound property to null when an input field is cleared.
In contrast to C#, Preview 2 brings several notable additions to the F# programming language. The language gains support for the #elif preprocessor directive, eliminating the need for deeply nested conditional compilation blocks. A new partitionWith function has been added across core collection types, allowing as-explained collections to be split into two groups of different element types.
A new overload resolution caching mechanism is reported to reduce type-checking time from 6.5 seconds to 2.9 seconds in tested benchmarks. All 462 functions across core collection modules now also include Big-O complexity notes visible directly in IDE tooltips.
Other changes in this release include a generic GetTypeInfo for System.Text.Json, tar archive format selection, and, as reported 15 percent performance improvement to Matrix4x4.GetDeterminant.
For interested readers, the full release notes are available on the official .NET blog and the dotnet GitHub repository.