Exploring .NET 11 Preview 4: Key Features and Improvements

Welcome to the fourth preview of .NET 11, packed with enhancements across the runtime, SDK, libraries, ASP.NET Core, .NET MAUI, C#, and Entity Framework Core. In this Q&A, we break down the most notable updates, helping you understand what's new and how to get started. Let's dive into the details.

1. What major updates are included in the .NET libraries for Preview 4?

The .NET libraries receive significant updates in this release. The Process class gets its biggest overhaul in years, improving performance and flexibility. New span-based APIs for Deflate, ZLib, and GZip encoders/decoders enable zero-allocation compression scenarios. Additionally, floating-point hex formatting and parsing support provides consistent handling across numeric types. System.Text.Json also gets improvements to enhance serialization performance and usability. These library changes make .NET 11 more efficient for high‑throughput applications and modern data processing tasks.

2. How does the .NET 11 runtime improve performance?

The runtime enhancements center on three main areas. First, runtime libraries are now compiled with runtime-async, which optimizes async code paths for reduced overhead. Second, the JIT compiler introduces new optimizations that accelerate execution, especially for loops and hot code. Third, hardware intrinsics and code generation have been refined to take better advantage of CPU features like AVX-512. These changes collectively boost throughput and lower latency, particularly in compute‑intensive scenarios such as scientific computing and real‑time analytics.

3. What new features does the .NET SDK bring in Preview 4?

The SDK gains several quality‑of‑life improvements. dotnet watch now supports device selection for .NET MAUI and mobile projects, streamlining the development of cross‑platform applications. Fish shell completions have been added, matching existing support for Bash, Zsh, and PowerShell, making command‑line work more efficient. Commands like dotnet reference now fall back to the current directory when no path is specified, reducing keystrokes. Finally, the SDK replaces Application Insights with OpenTelemetry for CLI telemetry, aligning with broader industry standards for observability.

4. What C# language enhancements are included in this preview?

C# updates focus on developer experience and build performance. A clearer diagnostic message is provided for misplaced #! shebang directives, helping Linux/macOS users identify syntax errors earlier. Additionally, an opt-in compilation cache for the VBCSCompiler build server speeds up incremental rebuilds, especially in large projects. These changes reduce friction during development and shorten edit‑compile‑debug cycles.

5. How has ASP.NET Core evolved in .NET 11 Preview 4?

ASP.NET Core introduces several enhancements. The HTTP QUERY method is now supported in generated OpenAPI documents, enabling better RESTful API design. Blazor gains SupplyParameterFromTempData to persist state across redirects, simplifying multi‑step workflows. A server‑initiated Blazor Server circuit pause allows applications to reduce resource usage during idle periods. Notably, the MCP Server template now ships with the .NET SDK, making it straightforward to build custom tool servers for AI‑assisted development.

6. What does .NET MAUI offer for mobile developers in this preview?

.NET MAUI developers benefit from dotnet watch support for both Android and iOS hot reload scenarios. This means you can edit XAML or C# files and see changes reflected live on emulators or physical devices without restarting the app. The device selection feature (also part of the SDK) lets you choose which target device to deploy to, streamlining the testing workflow. These updates significantly shorten the feedback loop when building cross‑platform mobile applications with .NET MAUI.

7. What are the key Entity Framework Core updates in Preview 4?

Entity Framework Core gains several notable features. Approximate vector search is now available for SQL Server 2025, enabling semantic similarity queries over high‑dimensional data. JSON mapping is fully integrated into the relational model, allowing you to store and query JSON documents more naturally. Temporal period properties (for history tracking) can now be mapped to CLR properties, giving you direct access to time‑related data. Finally, the dotnet ef tool reads defaults from a dotnet-ef.json file, simplifying configuration across projects.