Microsoft has officially rolled out .NET 9, marking a significant upgrade in its open-source development platform with key improvements in performance, cloud-native application support, and advanced AI functionality. This latest version boosts tools and frameworks like ASP.NET Core, Aspire, Blazor, MAUI, C#, and F#, enabling developers to create more efficient and intelligent applications.

Available for download as of November 12, .NET 9 introduces over a thousand updates focused on optimizing performance across runtime, workloads, and languages. Microsoft has revamped the Server Garbage Collector (GC) to dynamically adjust memory allocation based on application demands rather than fixed environmental resources. Additionally, the runtime benefits from hardware acceleration with support for Arm64 SVE and Intel AVX10 and has returned to vectorization for further computational efficiency. Enhanced Dynamic Profile Guided Optimization (PGO) refines code by targeting more common patterns, streamlining applications for improved runtime performance.

In the AI domain, .NET 9 includes a robust suite for integrating AI features into applications. With the help of Semantic Kernel, Microsoft has added the Microsoft.Extensions.AI and Microsoft.Extensions.VectorData libraries, creating a unified API layer for developers working with language models, embeddings, and vector databases. These tools facilitate the inclusion of AI components such as small and large language models (SLMs and LLMs) and middleware, making AI integration smoother and more versatile.

The cloud stack, .NET Aspire, also sees notable improvements in .NET 9. Developers can now manage resources more seamlessly through dashboard enhancements that include features for resource start/stop functionality, container persistence, and access to new APIs like WaitFor, which optimizes resource loading and management.

The release also brings advancements in the C# and F# languages:

• C# 13: This update focuses on enhancing code efficiency and readability. New features include expanded use of the params modifier, allowing a wider range of collections in method signatures, and new ways to work with ref struct values for high-performance scenarios. Improvements in multi-threaded application support, such as System.Threading.Lock, further optimize code for concurrency.
• F# 9: Updates in F# prioritize safety and efficiency, with features like nullable reference types that improve type safety in cross-language work with C#. Performance enhancements in integral ranges and optimized equality checks help streamline common operations.

The ASP.NET Core web framework gains security-focused improvements, with tools to easily enable HTTPS during development on Linux and optimized static assets for more efficient deployment. Enhanced monitoring and reduced memory usage ensure smoother, more reliable web applications.

Blazor, Microsoft’s web framework for building interactive applications, now includes a new solution template for creating cross-platform apps with shared UI across .NET MAUI and Blazor. Blazor also introduces the RendererInfo API, which detects component rendering modes at runtime, offering flexible and efficient client-server rendering.

Windows app developers gain streamlined access to the latest OS features with .NET 9, which incorporates OpenAPI document generation via the Microsoft.AspNetCore.OpenAPI package. Additionally, a new template for .NET MAUI includes several Syncfusion controls and libraries for database access, navigation, and other standard app patterns.

With .NET 9, Microsoft has equipped developers with powerful tools for building faster, smarter, and more secure applications across cloud and on-premises environments, reinforcing .NET’s position as a versatile platform for modern software development.