Everything You Need to Know About .NET 11 Preview 4: A Q&A Guide

Welcome to our comprehensive Q&A guide for .NET 11 Preview 4! This release brings a wave of improvements across the .NET ecosystem, from the runtime and libraries to ASP.NET Core, MAUI, and Entity Framework Core. We've compiled the most important updates into seven questions and answers to help you quickly grasp what's new and how it can benefit your development workflow. Jump to any section using the links below.

Library Updates
Runtime Improvements
SDK Enhancements
C# Changes
ASP.NET Core Updates
.NET MAUI Updates
Entity Framework Core Updates

What are the major library updates in .NET 11 Preview 4?

The libraries have received some significant enhancements. For instance, the Process class gets its biggest update in years, providing deeper control and monitoring capabilities for system processes. Additionally, new Span-based encoder/decoder APIs for Deflate, ZLib, and GZip are now available, allowing for more efficient memory handling and better performance. Floating-point formatting and parsing now supports hexadecimal representations, which is particularly useful for debugging and interoperability. On top of that, System.Text.Json continues to improve with minor fixes and optimizations. These updates collectively make .NET more performant and developer-friendly, especially in scenarios involving data compression and serialization.

Everything You Need to Know About .NET 11 Preview 4: A Q&A Guide — Source: devblogs.microsoft.com

How does the runtime improve with Preview 4?

The runtime libraries are now compiled with runtime-async, a new compilation mode that reduces startup times and memory consumption. The JIT compiler also introduces several optimizations, such as better inlining decisions and improved code generation for hot paths. Hardware intrinsics have been expanded, allowing developers to leverage CPU-specific instructions more easily, which can lead to significant performance gains in computationally intensive tasks. Code generation has also been refined to produce smaller and faster native code. Overall, these runtime enhancements aim to deliver a smoother experience for both application users and developers, especially in cloud and high-performance environments.

What new features does the SDK introduce?

The SDK brings several quality-of-life improvements. dotnet watch now supports device selection for .NET MAUI and mobile projects, making it easier to target specific physical devices or emulators during development. Fish shell completions have been added, matching the existing support for Bash, Zsh, and PowerShell, so Fish users get the same level of auto-completion. Commands like dotnet reference now fall back to the current directory when no project is specified, reducing typing overhead. In a significant telemetry change, OpenTelemetry replaces Application Insights for CLI telemetry, aligning .NET with industry standards for observability. These updates streamline the developer experience, especially for cross-platform and mobile developers.

What changes are there in C# for this preview?

The C# compiler receives two notable refinements. First, diagnostics for misplaced shebang (#!) directives are now clearer. Shebang directives are used to make scripts executable on Unix-like systems, and now the compiler gives more helpful error messages if they appear in incorrect positions. Second, the VBCSCompiler build server gains an opt-in compilation cache, which can speed up incremental builds by caching compiled results. This feature is optional and can be enabled to reduce build times in large solutions. These changes may seem small, but they improve the daily workflow for C# developers, especially those working on cross-platform scripts or large enterprise projects.

What enhancements does ASP.NET Core bring?

ASP.NET Core adopts the HTTP QUERY method in generated OpenAPI documents, enabling better interoperability with APIs that use this HTTP method. For Blazor developers, there's a new SupplyParameterFromTempData attribute that simplifies passing temporary data between pages without manual storage. Additionally, developers can now initiate a server-initiated Blazor Server circuit pause, giving them greater control over circuit lifecycle. Perhaps most exciting is the inclusion of the MCP Server template directly in the .NET SDK, allowing quick scaffolding of Model Context Protocol servers. These features enhance ASP.NET Core's capabilities for building modern, real-time web applications.

How does .NET MAUI benefit from Preview 4?

.NET MAUI developers can now leverage dotnet watch for both Android and iOS development. This means you can run your MAUI app on a device or emulator, and any code changes automatically trigger a hot reload, significantly speeding up the iteration cycle. Previously, dotnet watch was limited to other project types, so this addition is a game-changer for mobile developers. Combined with the new device selection feature in the SDK (covered earlier), it makes debugging and testing MAUI applications much more efficient. These updates bring .NET MAUI closer to parity with web development workflows in terms of developer productivity.

What's new in Entity Framework Core for Preview 4?

EF Core introduces approximate vector search support for SQL Server 2025, enabling AI-driven similarity queries on vector data—a big step for modern app scenarios. JSON mapping is now fully integrated into the relational model, meaning you can map JSON documents directly to database columns with first-class support in LINQ queries. Temporal period properties (like ValidFrom and ValidTo) can now be mapped to CLR properties, giving more control over temporal tables. Lastly, the dotnet ef tool reads default settings from a dotnet-ef.json file, simplifying configuration. These features make EF Core more powerful for handling complex data models and modern database capabilities.

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