Preview 6 of Microsoft’s .NET 11 software development platform is now available, with improvements across the runtime, libraries, frameworks, and C# and F# programming languages.

Announced July 14, .NET 11 Preview 6 can be downloaded from dotnet.microsoft.com. The full, general production release is expected in November. The first preview was unveiled February 10.

Runtime-async, the .NET runtime’s built-in implementation of async/await, keeps getting faster in Preview 6, building on the suspension improvements from Preview 5. Async continuations can now opt out of ExecutionContext capture and restore. And the JIT now compiles a dedicated runtime-async version of a synchronous, task-returning method rather than delegating to it through a thunk. The JIT turns the method’s tail calls into runtime-async calls and awaits the task that would otherwise have been returned, so the async path no longer pays for an extra layer of indirection, Microsoft said.

In library improvements, System.Text.Json can now serialize and deserialize the new C# union types. The serializer recognizes a union through the new JsonTypeInfoKind.Union contract type, reads and writes the active case, and supports the reflection-based serializer and the source generator. The new JsonUnionAttribute, JsonUnionCaseInfo, and type-classifier APIs enable customization of how cases are discovered and named.

In C# improvements, extension members now include indexers, so developers can add this[...] access to a type from an extension block. This rounds out the extension members feature introduced in .NET 10, which already supported extension methods and properties. An extension indexer is declared like an instance indexer inside an extension block.

Other highlights in .NET 11 Preview 6:

• Math.BigMul(long, long, out long) is now significantly faster on x64. The JIT generates a single MUL r/m64 instruction when both operands are 64-bit values and the caller requests the high half of the result. Previously the JIT emitted a helper call. The change eliminates the call overhead and makes code that multiplies large numbers tighter.
• Minimal API validation in ASP.NET Core now supports asynchronous validators end-to-end.
• For F#, the compiler emits better sequence points for several common debugging scenarios. Breakpoints and stepping are improved for call arguments that need stack-empty debug points, for expressions and comprehensions, simple literal bindings, and if or match conditions.
• For .NET MAUI, .NET 11 Preview 6 advances the cross-platform CollectionView and Shell architecture, removes the legacy Xamarin.Forms compatibility package, and brings the Apple workloads onto stable Xcode 26.6.
• Also for .NET MAUI, HybridWebView JavaScript interop is reworked to use a source generator instead of reflection, so it no longer produces trim or AOT (ahead of time) compiler warnings and works correctly in fully trimmed and Native AOT apps.
• Projects that use Microsoft.TypeScript.MSBuild in Razor Class Libraries now properly integrate TypeScript compilation outputs with ASP.NET Core Static Web Assets.

Microsoft has released TypeScript 7.0, a native port of the company’s strongly typed version of the JavaScript language based on the Go programming language.

With this new codebase, TypeScript 7.0 brings native code speed, shared memory multithreading, and a number of new optimizations that typically yield speedups between 8x and 12x on full builds, Microsoft said in a July 8 announcement. This port of TypeScript to native code was done as faithfully as possible, writing new code while maintaining the structure and logic of the original codebase to keep results consistent and compatible between the two compilers, according to Microsoft. 

TypeScript 7.0 is available via npm:

npm install -D typescript

To help with the TypeScript 6.0 to TypeScript 7.0 transition process, Microsoft has published a new compatibility package, @typescript/typescript6. This package provides an executable named tsc6, so that if needed, a developer can install TypeScript 7.0 (which ships its own tsc binary) side-by-side with TypeScript 6.0 without naming conflicts. The new package also re-exports the TypeScript 6.0 API, so that a developer can use tsc for TypeScript 7, while other tooling can continue to rely on TypeScript 6.0.

TypeScript 7.0 is a major milestone in the TypeScript project, Microsoft said. This port has been the primary focus for Microsoft’s team for more than a year. With TypeScript 7.0 now out, the team will return to new feature work, ergonomic improvements, more performance wins, and implementing a new API for the broader ecosystem. Microsoft expects a fairly similar timeline to releases prior to TypeScript 7.0, with new versions published every three to four months.

TypeScript 7.0 was announced as a release candidate on June 18.