What’s New in .NET 9 Preview 6: Comprehensive Overview

#csharp #dotnet #devtoys

On July 9th, 2024, Microsoft released .NET 9 Preview 6, featuring significant updates and enhancements across the framework. Key highlights include:

Runtime Updates:

ARM64 Code Generation: Improved data loading/storing, enhancing execution time.
Code Layout: Optimized basic block ordering for better performance.
Loop Optimizations: Enhanced performance by flipping loop counter variables.
Reduced Address Exposure: Better tracking of local variables for more optimizations.
AVX10v1 Support: New SIMD instruction set for AVX10-enabled hardware. Hardware Intrinsic Code Generation: Improved handling of constants in hardware intrinsics.
Constant Folding: Enhanced for floating-point and SIMD operations.

Quality Improvements: Expanded test coverage and bug fixing for Android and iOS development.
ASP.NET Core Updates:
Fingerprinting of Static Web Assets: Improved caching and load times.
Enhanced Distributed Tracing for SignalR: Better tracing capabilities.
Microsoft.AspNetCore.OpenAPI Enhancements: Improved attribute support and schema transformers.
New Analyzer for [Authorize] and [AllowAnonymous]: Warns when [Authorize] is overridden.

Partial Properties: Supports source generators, making APIs intuitive.
Primary Constructors in Logging Source Generator: Logging using classes with primary constructors.
System.Text.Json Updates:
Respecting Nullable Annotations: Enforces nullability during serialization/deserialization.
Requiring Non-Optional Constructor Parameters: Treats non-optional constructor parameters as required.
Ordering JsonObject Properties: Enables explicit property order manipulation.
Additional Contract Metadata APIs: Exposes constructor metadata and improved attribute support.

[GeneratedRegex] on Properties: Supports partial properties in C# 13.
Regex.EnumerateSplits: Span-based input without allocation.
OrderedDictionary: New generic collection.
ReadOnlySet: For creating read-only views of sets.
Span-Based APIs: New features for file operations and string manipulations.
Base64Url: Methods for Base64Url encoding/decoding. SocketsHttpHandler by Default: Improved configurability in HttpClientFactory.
TLS Resume with Client Certificates on Linux: Adds support for TLS resume on Linux.
Metrics Gauge Instrument: Records non-additive values like background noise level.