.NET 9 Release

Microsoft has announced the release of .NET 9, marking a significant evolution in their development platform with thousands of improvements across the framework. This release represents the continued unification of .NET Framework, .NET Core, and Mono, enabling developers to create cross-platform applications for browsers, cloud systems, desktops, IoT devices, and mobile platforms using unified libraries and a common build process.

I highly recommend at least skimming this article to stay up to date with the changes.

Core Runtime Improvements

The .NET 9 release includes substantial performance optimizations in several key areas:

- Enhanced Garbage Collection: Implemented a dynamic adaptation mechanism that adjusts based on application size rather than available system resources. This improvement particularly benefits applications running on multi-core systems with varying memory requirements.

- JIT Compiler Enhancements:

- Added new Profile-Guided Optimization (PGO)

- Improved loop processing and inline expansion

- Enhanced boundary checking

- Added support for Arm64 SVE and Intel AVX10 vector instructions

- 50% faster exception handling code

- Up to 70% performance improvement for type-casting operations

- LINQ Optimization: Methods like Take and DefaultIfEmpty show up to 10x performance improvement when working with empty arrays and collections.

- JSON Processing: System.Text.Json improvements show 15% higher throughput and 93% lower memory usage in TechEmpower benchmarks compared to .NET 8.

Development Tools and Language Features

C# 13 Enhancements

- Extended params modifier support for collections beyond arrays

- New escape sequence "\e"

- Support for "^" operator in array initialization

- Ref and unsafe expressions allowed in iterators and async methods

- Interface definitions for "ref struct" types

- New Lock type for thread synchronization

F# 9 Features

- Null-capable types support

- Auto-generated ".Is*" properties in unions

- Empty computed expressions support

- Non-string values in "#" directives

- Random selection and shuffling functions in List, Array, and Seq modules

Cloud and AI Integration

.NET Aspire

- New stack for cloud-native application development

- Enhanced resource management and application lifecycle controls

- Expanded telemetry collection capabilities

- Improved integration with cloud services

AI Development

- New C# abstractions for AI application development

- Tensor operations and vector computations

- Integration with large language models

- Vector storage interaction capabilities

- Updated ML.NET framework

- New Microsoft.ML.Tokenizers library

Web Development

ASP.NET Core Improvements

- Enhanced ahead-of-time compilation support

- Expanded monitoring and tracing capabilities

- Reduced startup time and memory consumption

- Optimized static file handling

- New authentication and authorization API

- Updated Blazor templates for hybrid and web applications

MAUI Framework Updates

- Performance optimizations

- Enhanced desktop and mobile application integration

- New interface elements: TitleBar and HybridWebView

- Improved theming support in WPF

SDK and Runtime Availability

The .NET 9 SDK, Runtime, and ASP.NET Core Runtime are available for:

- Linux

- macOS

- Windows

The .NET Desktop Runtime 9 is exclusively available for Windows platforms.

Developer Tools Integration

Visual Studio and Visual Studio Code have been updated to support .NET 9 and C# 13, providing developers with enhanced tooling capabilities and improved development experience. The platform continues to maintain its open-source nature, with related developments including .NET Runtime and SDK published on GitHub under the MIT license.

This release represents a significant step forward in Microsoft's development ecosystem, offering developers improved performance, enhanced AI capabilities, and better tools for building modern applications across multiple platforms.