.NET 11 Preview 4: Everything You Need to Know

Welcome to .NET 11 Preview 4! This latest milestone brings significant enhancements across the entire ecosystem—from the runtime and SDK to ASP.NET Core, .NET MAUI, C#, and Entity Framework Core. Whether you're building cloud services, mobile apps, or desktop tools, this release includes performance gains, new APIs, and developer experience improvements that make your workflow smoother. Below, we answer the key questions about what's new and how to get started. Use the links to jump to your area of interest.

What major library updates are in Preview 4?

The Libraries area receives its most substantial overhaul in years. The Process class gets a major update, introducing more efficient process management and diagnostics. You'll also find new Span-based APIs for Deflate, ZLib, and GZip encoders/decoders, which improve performance in compression scenarios by reducing allocations. Floating-point handling gets a boost with hex formatting and parsing, enabling precise numeric representations. System.Text.Json improvements include better support for custom converters and faster serialization. These updates are designed to make your code more performant and easier to write.

.NET 11 Preview 4: Everything You Need to Know — Source: devblogs.microsoft.com

How has the .NET runtime been improved?

The runtime libraries are now compiled with runtime-async, which optimizes asynchronous code paths for lower overhead. JIT optimizations continue with smarter inlining and loop optimizations, especially for hot paths. Hardware intrinsics and code generation improvements leverage CPU features more effectively, giving you native-level performance for math and data processing tasks. The team also refined the garbage collector and thread pool to reduce latency in high-throughput applications. All these changes happen transparently—just compile your app and see the speed benefits.

What new features does the SDK bring?

Several SDK enhancements target both mobile and command-line workflows. dotnet watch now supports device selection for .NET MAUI and mobile projects, so you can pick which emulator or physical device to deploy to directly from the CLI. Fish shell completions are now on par with Bash, Zsh, and PowerShell, making it easier to discover commands. The commands dotnet reference and similar now fall back to the current directory if no project is specified, reducing typing. Telemetry has shifted from Application Insights to the open-source OpenTelemetry, giving you more control over data. These changes streamline day-to-day development.

What changes are there for C# developers?

C# gains quality-of-life improvements. The compiler now provides clearer diagnostics for misplaced #! shebang directives, which are commonly used in scripts. This means you'll see more actionable error messages when a shebang appears in an unexpected location. Additionally, the VBCSCompiler build server can now opt into a compilation cache to reuse compiled results across builds, speeding up your inner loop. These enhancements are invisible but make the developer experience smoother, especially when working on large solutions or cross-platform scripts.

What's new in ASP.NET Core with this preview?

ASP.NET Core expands its Web API and Blazor capabilities. The HTTP QUERY method is now supported in generated OpenAPI documents, aligning with HTTP standards for safe, idempotent queries. Blazor gets SupplyParameterFromTempData to preserve state across redirects, useful for wizard-style pages. For long-running connections, server-initiated Blazor Server circuit pause allows the server to suspend inactive circuits, saving resources. Also, the MCP Server template now ships with the .NET SDK, making it easy to build Model Context Protocol servers—great for AI integrations. These updates keep .NET at the forefront of modern web development.

How does Preview 4 enhance .NET MAUI development?

Mobile developers get a productivity boost with dotnet watch support for Android and iOS. Previously limited to desktop projects, the hot reload feature now works seamlessly on physical devices and emulators. You can edit code and see changes instantly without restarting the app—a huge time-saver for UI tweaks and debugging. The device selection we mentioned earlier lets you target a specific device right from the command line, paired with the appropriate framework. Combined with the new dotnet watch integration, building cross-platform mobile apps feels as fast as web development.

What updates are included for Entity Framework Core?

Entity Framework Core brings cutting-edge database features. Approximate vector search is now supported for SQL Server 2025, enabling efficient similarity searches in AI and machine learning scenarios. JSON mapping is fully integrated into the relational model, so you can map JSON columns directly to .NET types without extra ceremony. Temporal period properties (like ValidFrom/ValidTo) can now be mapped to regular CLR properties, simplifying time-tracking queries. Additionally, dotnet ef reads defaults from a dotnet-ef.json file, making it easier to configure scaffolding and migrations across teams. These features make EF Core more powerful and convenient.

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