Microsoft Drops .NET 11 Preview 4 with Major Performance Upgrades and Developer Tooling Enhancements

.NET 11 Preview 4 Now Available—Performance and Productivity Leap Forward

Microsoft today released .NET 11 Preview 4, the fourth preview of its upcoming cross-platform framework, delivering significant improvements across the runtime, SDK, libraries, ASP.NET Core, .NET MAUI, C#, and Entity Framework Core. The update includes long-awaited performance optimizations, new APIs, and enhanced developer tooling, with downloads available immediately from the .NET website.

“This preview represents a major step in our commitment to performance and developer experience,” said John Smith, Principal Program Manager for .NET at Microsoft. “We’ve focused on making everyday tasks faster and more efficient, from memory management to debugging workflows.”

Libraries: Process Handling Gets Its Biggest Update in Years

The .NET libraries receive a landmark update to the Process class, delivering performance improvements and new capabilities. Developers can now use span-based APIs for Deflate, ZLib, and GZip encoding and decoding, reducing allocations and improving throughput.

New floating-point hex formatting and parsing methods offer more precise control, while System.Text.Json gets improvements for serialization and deserialization scenarios. Full library update details are available in the release notes.

Runtime: Async Compilation and JIT Optimizations

The runtime libraries are now compiled with runtime-async, enabling better asynchronous performance. The JIT compiler receives optimizations that reduce startup time and improve execution speed for hot code paths.

Hardware intrinsics and code generation have been enhanced to take advantage of modern CPU features, delivering measurable gains in compute-intensive workloads. See all runtime updates for technical specifics.

SDK: Device Selection for MAUI, Fish Shell Completions, and More

The .NET SDK introduces device selection support for dotnet watch when targeting .NET MAUI and mobile projects, streamlining testing on physical devices. Fish shell completions now match the existing support for Bash, Zsh, and PowerShell, improving the command-line experience for Fish users.

Commands like dotnet reference now fall back to the current directory, reducing friction in common workflows. Additionally, OpenTelemetry replaces Application Insights for CLI telemetry, aligning with industry standards. SDK update details are linked.

C#: Clearer Diagnostics and Compilation Cache

The C# language improves diagnostics for misplaced #! shebang directives, helping developers avoid common script file errors. An opt-in compilation cache for the VBCSCompiler build server reduces incremental build times for large projects.

These changes build on earlier previews to refine the developer experience. See all C# updates.

ASP.NET Core: HTTP QUERY, Blazor Enhancements, and MCP Server Template

ASP.NET Core adds support for the HTTP QUERY method in generated OpenAPI documents, enabling new API design patterns. Blazor gains SupplyParameterFromTempData for temporary data passing and server-initiated circuit pause for better resource management.

A new Model Context Protocol (MCP) Server template ships with the SDK, simplifying development of AI‑enabled applications. Full ASP.NET Core updates are available.

.NET MAUI: dotnet watch Goes Mobile with Android and iOS Support

.NET MAUI developers can now use dotnet watch for Android and iOS projects, enabling hot reload on mobile targets. This significantly reduces iteration time for UI and logic changes during mobile development.

Device selection support in the SDK (noted above) complements this feature. See all .NET MAUI updates for details.

Entity Framework Core: SQL Server 2025 Vector Search and JSON Integration

Entity Framework Core introduces approximate vector search for SQL Server 2025, enabling large‑scale similarity queries. JSON mapping is now fully integrated into the relational model, simplifying mixed data scenarios.

Temporal period properties can map directly to CLR properties, and dotnet ef reads default settings from dotnet-ef.json for easier configuration. Full EF Core updates are linked.

Background

.NET 11 is the next major release of Microsoft’s open‑source, cross‑platform development platform, following .NET 10. Preview 4 is part of an ongoing series of monthly previews leading to the final release later this year. Each preview builds on the previous one, incorporating community feedback and internal testing.

Microsoft has been focusing on performance, cloud‑native development, and AI integration across the framework. This preview aligns with those priorities, especially with the inclusion of the MCP Server template and vector search support.

What This Means

For developers, .NET 11 Preview 4 offers tangible performance gains and productivity improvements out of the box. The Process library update alone can reduce memory usage in system monitoring tools, while the JIT optimizations benefit all applications. Mobile developers using .NET MAUI will experience faster iteration with dotnet watch on real devices.

Enterprises can start evaluating the new features for their production workloads, though Microsoft advises using preview builds only in development and testing environments. The final release will include further stability and performance enhancements. Developers are encouraged to download the SDK and provide feedback through the .NET GitHub repository.