7 Game-Changing Updates in .NET 11 Preview 4 You Should Know

Microsoft has just released .NET 11 Preview 4, packed with improvements across the entire ecosystem—from the runtime and libraries to ASP.NET Core and .NET MAUI. Whether you're a web developer, mobile developer, or backend engineer, this preview brings tools and performance boosts that will streamline your workflow. Here are the top 7 highlights that stand out in this release.

• 1. Libraries: Big Updates and New APIs
• 2. Runtime: Async Compilation and JIT Enhancements
• 3. SDK: Smarter Tooling and Telemetry Changes
• 4. C#: Better Diagnostics and Build Cache
• 5. ASP.NET Core: Blazor and OpenAPI Innovations
• 6. .NET MAUI: Enhanced Mobile Development with dotnet watch
• 7. Entity Framework Core: SQL Server 2025 and JSON Integration

1. Libraries: Big Updates and New APIs

The System.Diagnostics.Process class received its most significant update in years, offering improved management of process lifetime and capabilities. Additionally, new Span-based Deflate, ZLib, and GZip encoder/decoder APIs allow for more efficient compression and decompression without allocating extra memory. Floating-point formatting and parsing now support hexadecimal strings, which helps with precise numeric debugging and serialization. System.Text.Json also gets notable improvements for better performance and flexibility. These library changes are foundational—affecting every .NET application. For more on the runtime side, see Item 2.

2. Runtime: Async Compilation and JIT Enhancements

The runtime itself is now compiled using a new runtime-async approach, meaning many internal library components are built to be asynchronous from the ground up, reducing thread blocking. JIT optimizations continue to improve, with better handling of hot code paths and reduced overhead. Hardware intrinsics and code generation have also been refined, enabling developers to leverage SIMD and other CPU features more effectively. These changes lead to faster execution and lower latency for critical workloads. Combined with the library updates, the runtime makes .NET 11 Preview 4 a compelling upgrade for performance-sensitive applications.

3. SDK: Smarter Tooling and Telemetry Changes

The dotnet watch command now supports device selection specifically for .NET MAUI and mobile projects, making it easier to target Android or iOS emulators and physical devices during development. Fish shell completions have been added, matching the existing Bash, Zsh, and PowerShell support. Commands like dotnet reference now fall back to the current directory automatically if no path is specified, reducing typing. Additionally, OpenTelemetry replaces Application Insights as the default for CLI telemetry, aligning with industry standards. These improvements enhance productivity and modernize the developer experience—check out the runtime enhancements in Item 2 for complementary performance gains.

4. C#: Better Diagnostics and Build Cache

C# gains clearer diagnostic messages for misused #! shebang directives, helping developers quickly fix script-style files. An opt-in compilation cache for the VBCSCompiler build server reduces rebuild times by reusing previously compiled assemblies. This is especially beneficial for large solutions where incremental builds are common. While not a language feature per se, these changes improve the overall C# development pipeline. For a deeper look at how these fit into the SDK ecosystem, see Item 3.

5. ASP.NET Core: Blazor and OpenAPI Innovations

ASP.NET Core now includes support for the HTTP QUERY method in generated OpenAPI documents, which is useful for idempotent data retrieval without side effects. Blazor gets a new SupplyParameterFromTempData attribute to pass data across requests, and server-side Blazor circuits can now be paused by the server for better resource management. Additionally, an MCP Server template ships with the .NET SDK, enabling quick creation of Machine Control Protocol services. These additions expand ASP.NET Core's versatility for modern web scenarios. For mobile development capabilities, see Item 6.

6. .NET MAUI: Enhanced Mobile Development with dotnet watch

Both Android and iOS developers can now use dotnet watch for hot reload during development, dramatically improving the edit-and-run cycle. This feature allows you to see changes immediately without manual rebuilds and redeployments. Combined with the device selection added in the SDK (see Item 3), .NET MAUI becomes even more productive for cross-platform mobile apps. While this preview focuses on these two platforms, it sets the stage for broader watch support in future releases.

7. Entity Framework Core: SQL Server 2025 and JSON Integration

Entity Framework Core introduces approximate vector search for SQL Server 2025, enabling efficient similarity searches in AI and machine learning scenarios. JSON mapping is now fully integrated into the relational model, allowing you to work with JSON columns using familiar EF Core patterns. Temporal period properties can map directly to CLR properties, simplifying time‑based queries. Additionally, dotnet ef reads default settings from dotnet-ef.json, reducing boilerplate. These features make EF Core more powerful for modern data‑driven applications.

Conclusion

.NET 11 Preview 4 delivers meaningful improvements across the board—from the library layer to the runtime, tooling, and frameworks. Whether you’re building web APIs, mobile apps, or microservices, this preview gives you a taste of what’s coming in the final release. To get started, download the .NET 11 SDK. On Windows, use Visual Studio 2026 Insiders; otherwise, Visual Studio Code with C# Dev Kit works perfectly. We encourage you to test these features and share feedback—every preview shapes the final product!