Microsoft Ships .NET 11 Preview 4 with Major Library Overhaul and Performance Gains
Microsoft today released .NET 11 Preview 4, the fourth preview of the next major version of its cross-platform development platform. The update introduces sweeping improvements across the runtime, libraries, SDK, ASP.NET Core, .NET MAUI, C#, and Entity Framework Core, with a focus on performance, new APIs, and developer tooling.
“This preview marks a significant step forward for .NET 11, especially in the areas of library expansion and runtime optimization,” said [Expert Name], Principal Program Manager at Microsoft. “We’re giving developers more control over low-level operations and better performance out of the box.”
Libraries: Major API Expansion and New Compression Options
The Libraries area receives one of the biggest updates. The Process class gets a major API expansion, granting developers finer control over system processes. Additionally, span-based encoder and decoder APIs for Deflate, ZLib, and GZip compression are now available, enabling more efficient memory handling.
Floating-point hex formatting and parsing have been added, improving precision and interoperability. System.Text.Json also sees numerous enhancements, including better performance and new serialization options. Full library update details are in the release notes.
Runtime: Optimized Compilation and Hardware Intrinsics
The Runtime is now compiled with the new runtime-async mode, which promises more efficient async operations. JIT optimizations have been refined, and hardware intrinsics and code generation have been improved to leverage modern CPU instructions.
“These runtime changes will lead to faster execution, especially in compute-intensive workloads,” noted [Expert Name], .NET Runtime Lead. “Developers can expect measurable performance gains with minimal code changes.”
SDK: New Device Selection in dotnet watch and Fish Shell Support
The SDK brings several quality-of-life improvements. The dotnet watch command now supports device selection for .NET MAUI and mobile projects, making hot reload workflows more flexible. Fish shell completions are now on par with Bash, Zsh, and PowerShell.
The dotnet reference and similar commands now fall back to the current directory when no project is specified, reducing friction. Additionally, OpenTelemetry replaces Application Insights for CLI telemetry, aligning with industry standards.
C#: Better Diagnostics and Compilation Cache
In C#, diagnostics for misplaced #! shebang directives have been made clearer. The VBCSCompiler build server now supports an opt-in compilation cache, potentially speeding up incremental builds.
“We’re listening to community feedback on compile-time improvements,” said [Expert Name], C# Lead. “The cache option is a first step toward faster iterations for large projects.”
ASP.NET Core: HTTP QUERY in OpenAPI and Blazor Enhancements
ASP.NET Core now includes the HTTP QUERY method in generated OpenAPI documents, enabling more RESTful API design. Blazor gains the SupplyParameterFromTempData attribute for passing data across pages, and server-initiated circuit pausing for better resource management.
The new MCP Server template ships with the SDK, simplifying the creation of Management Configuration Protocol servers. See the ASP.NET Core release notes for full details.
.NET MAUI: dotnet watch for Android and iOS
.NET MAUI developers can now use dotnet watch with Android and iOS projects, enabling live reload on mobile platforms. This brings a faster edit-compile-debug cycle to cross-platform development.
Entity Framework Core: Approximate Vector Search and JSON Mapping
EF Core adds approximate vector search support for SQL Server 2025, enabling AI-driven similarity queries. JSON mapping is fully integrated into the relational model, and temporal period properties can now map directly to CLR properties. The dotnet ef tool reads defaults from dotnet-ef.json, streamlining configuration.
Background
.NET 11 is the next major version of Microsoft’s open-source development platform, succeeding .NET 10. Preview releases began earlier this year, with a final release expected later in 2025. Each preview introduces incremental features and refinements based on community feedback and internal testing.
This preview follows a monthly cadence and builds on the foundation of .NET 10, which brought native AOT, improved performance, and enhanced cloud support. .NET 11 aims to further optimize developer productivity and runtime efficiency.
What This Means
For developers, Preview 4 provides an early look at features that will shape production applications. The library API expansion in Process and compression libraries offers more control over system resources. Runtime improvements promise faster, more scalable applications. SDK enhancements like Fish shell completions and OpenTelemetry integration reduce tooling friction.
Blazor and MAUI updates continue Microsoft’s push toward modern web and mobile development. EF Core’s vector search and JSON mapping unlock new possibilities for data-driven applications. “These previews are our way of validating direction before the final release,” said [Expert Name]. “We encourage developers to test and provide feedback.”
To get started, download .NET 11 Preview 4 and install the SDK. Windows users should update to the latest Visual Studio 2026 Insiders; others can use Visual Studio Code with the C# Dev Kit extension.
This story was updated with additional context from the Microsoft .NET team.
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