What's New in .NET 11 Preview 4: A Comprehensive Overview
Introduction
Microsoft has officially released the fourth preview of .NET 11, bringing a host of enhancements across the runtime, SDK, libraries, ASP.NET Core, .NET MAUI, C#, and Entity Framework Core. This release continues the platform's evolution with performance boosts, developer tooling improvements, and new APIs. Below, we break down the key updates in each major area. For details, refer to the linked sections.
Libraries Enhancements
The libraries receive substantial updates in Preview 4, focusing on compression, numerical formatting, and JSON processing.
Process Class Gets a Major Overhaul
The Process class sees its most significant improvement in years, offering better performance and reliability for process management tasks.
Span-Based Compression APIs
New span-based encoder/decoder APIs for Deflate, ZLib, and GZip are now available. These provide memory-efficient, high-performance compression directly from span buffers.
Floating-Point Hex Formatting and Parsing
Developers can now format and parse floating-point numbers in hexadecimal notation, simplifying interoperability with systems that use hex float representations.
System.Text.Json Improvements
System.Text.Json receives continued refinements, including better handling of custom converters and performance optimizations for serialization scenarios.
For a complete list, see all library updates.
Runtime Updates
The .NET runtime is now compiled with runtime-async, enabling more efficient asynchronous execution pathways throughout the platform.
JIT Optimizations
Just-in-time compilation benefits from new optimizations that reduce code size and improve execution speed, particularly for hot paths.
Hardware Intrinsics and Code Generation
Enhancements to hardware intrinsics and code generation allow better utilization of modern CPU features, resulting in faster numerical and SIMD operations.
See all runtime updates.
SDK Improvements
The .NET SDK includes several developer experience upgrades in Preview 4.
dotnet watch Device Selection for Mobile
The dotnet watch tool now supports device selection for .NET MAUI and mobile projects, making it easier to target specific emulators or connected devices during development.
Fish Shell Completions
Fish shell users now enjoy tab completions on par with Bash, Zsh, and PowerShell, streamlining command-line workflows.
dotnet reference Fallback
Commands like dotnet reference now fall back to the current directory when no explicit project path is provided, reducing typing overhead.
OpenTelemetry Replaces Application Insights
CLI telemetry transitions from Application Insights to OpenTelemetry, offering a vendor-neutral, standardized approach to observability.
See all SDK updates.
C# Language Updates
C# receives two notable refinements in this preview.
Clearer Diagnostics for Shebang Directives
The compiler now provides more descriptive error messages when #! shebang directives are misplaced, helping script authors fix syntax issues faster.
Opt-In Compilation Cache for VBCSCompiler
The VBCSCompiler build server can now use an opt-in compilation cache to speed up incremental builds by reusing previously compiled outputs.
See all C# updates.
ASP.NET Core Updates
ASP.NET Core Preview 4 brings several new features for API documentation, Blazor, and server infrastructure.
HTTP QUERY in OpenAPI Documents
Generated OpenAPI documents now support the HTTP QUERY method, aligning with the latest HTTP specifications for safe, idempotent query operations.
SupplyParameterFromTempData for Blazor
Blazor components can now use SupplyParameterFromTempData to pass data across navigation steps, simplifying multi-page workflows.
Server-Initiated Blazor Server Circuit Pause
Blazor Server circuits can be paused from the server side, reducing resource usage for idle connections while preserving state.
MCP Server Template Ships with SDK
A new project template for MCP (Managed Communication Protocol) Server is included in the .NET SDK, accelerating the creation of secure, managed communication endpoints.
.NET MAUI Updates
Mobile development with .NET MAUI gains improved debugging and deployment workflows.
dotnet watch for Android and iOS
The dotnet watch tool now supports hot reload for Android and iOS projects, enabling rapid editing and testing cycles directly on devices or emulators.
Entity Framework Core Updates
EF Core Preview 4 introduces database-specific features and JSON mapping improvements.
Approximate Vector Search for SQL Server 2025
EF Core now supports approximate vector search for SQL Server 2025, enabling high-performance similarity searches in machine learning scenarios.
JSON Mapping Fully Integrated
JSON column mapping becomes a first-class part of the relational model, simplifying the storage and querying of JSON documents within relational tables.
Temporal Period Properties Map to CLR Properties
Temporal table period columns can now be exposed as regular CLR properties, making it easier to work with time-travel data in C#.
dotnet ef Reads Defaults from dotnet-ef.json
The dotnet ef tool automatically reads default settings from a dotnet-ef.json file, reducing manual configuration for common commands.
See all EF Core updates.
Get Started
To try .NET 11 Preview 4, download the .NET 11 SDK. Windows users with Visual Studio should install the latest Visual Studio 2026 Insiders. Alternatively, use Visual Studio Code with the C# Dev Kit extension for a full .NET 11 development experience.
Originally published on the .NET Blog.