Exploring the Latest Enhancements in .NET 11 Preview 4

Introduction

The .NET team has just released the fourth preview of .NET 11, bringing a host of improvements across the entire ecosystem. From the runtime and libraries to SDK tools and web frameworks, this update refines performance, developer experience, and platform capabilities. In this article, we'll dive into the key highlights of .NET 11 Preview 4, covering everything from major library overhauls to new ASP.NET Core features. Let's explore what's new and how you can get started.

Libraries

Process Gets a Major Update

The Process class receives its most significant overhaul in years, with enhanced performance and new capabilities for managing system processes. This update simplifies common tasks like starting, stopping, or querying processes, making it more efficient for developers working with system-level operations.

Span-Based Compression APIs

New span-based APIs for Deflate, ZLib, and GZip encoders and decoders are now available. These APIs reduce allocations and improve throughput when compressing or decompressing data, especially in high-performance scenarios such as streaming or large-file processing.

Floating-Point Hex Formatting and Parsing

Developers can now format and parse floating-point numbers in hexadecimal notation directly through standard APIs. This feature is particularly useful for debugging, serialization, and interoperability with systems that use hex representations of floats.

System.Text.Json Improvements

The popular JSON library gains additional enhancements, including better handling of custom converters and improved performance for serialization and deserialization. These changes make it even easier to work with JSON in modern .NET applications.

For a full list of library updates, check the official release notes.

Runtime

Runtime Libraries Compiled with Runtime-Async

The runtime libraries are now compiled using the new runtime-async approach, which improves asynchronous performance and reduces overhead in core runtime components. This change benefits all .NET applications by making async operations more efficient at the system level.

JIT Optimizations

The Just-In-Time (JIT) compiler receives several optimizations, including better inlining decisions and improved code generation for common patterns. These tweaks lead to faster startup times and reduced memory usage in many workloads.

Hardware Intrinsics and Code Generation

Enhancements to hardware intrinsics allow developers to leverage CPU-specific instructions more effectively. Coupled with refined code generation, this update helps .NET applications achieve native-level performance on modern processors.

Detailed runtime improvements are available in the runtime update notes.

SDK

dotnet watch Adds Device Selection for MAUI and Mobile

dotnet watch now supports selecting specific devices for .NET MAUI and mobile projects. This makes it easier to target a particular emulator or physical device during development, streamlining the hot-reload workflow.

Fish Shell Completions

Fish shell users now enjoy command-line completions that match the existing support for Bash, Zsh, and PowerShell. This fills a gap for developers on modern Unix-like systems who prefer the Fish shell.

dotnet reference and Related Commands

Commands like dotnet reference now fall back to the current directory when no explicit path is provided, reducing the need for manual navigation in project-management tasks.

OpenTelemetry Replaces Application Insights for CLI Telemetry

The .NET CLI's telemetry system has switched from Application Insights to OpenTelemetry, aligning with industry standards and improving data privacy. This change ensures that telemetry collection is more transparent and extensible.

All SDK updates are listed in the SDK release notes.

C#

Clearer Diagnostic for Misplaced Shebang Directives

The C# compiler now provides more precise error messages when #! shebang directives are placed incorrectly. This helps developers quickly fix script-style C# files that rely on interpreter directives.

Opt-In Compilation Cache for VBCSCompiler

An opt-in compilation cache for the VBCSCompiler build server reduces build times by reusing previously compiled results. This feature is particularly beneficial in continuous integration environments.

For all C# updates, refer to the C# changes log.

ASP.NET Core

HTTP QUERY in Generated OpenAPI Documents

ASP.NET Core now includes support for the HTTP QUERY method in automatically generated OpenAPI documents, enabling richer API definitions for query-like operations.

SupplyParameterFromTempData for Blazor

Blazor introduces the SupplyParameterFromTempData attribute, allowing components to receive data from temporary storage across requests. This simplifies state management in multi-page applications.

Server-Initiated Blazor Server Circuit Pause

Blazor Server now supports server-initiated circuit pauses, which helps manage resources in long-running applications by temporarily suspending inactive circuits.

MCP Server Template Ships with the .NET SDK

A new project template for MCP (Message Control Protocol) servers is included out of the box, making it easier to build custom protocol handlers directly from the command line.

See all ASP.NET Core updates in the ASP.NET Core release notes.

.NET MAUI

dotnet watch for Android

Hot reload for Android projects now works seamlessly with dotnet watch, allowing developers to see UI changes instantly without restarting the app.

dotnet watch for iOS

Similarly, dotnet watch support for iOS enables rapid iteration on mobile user interfaces, reducing development feedback loops for cross-platform apps.

Full .NET MAUI updates can be found in the MAUI release notes.

Entity Framework Core

Approximate Vector Search for SQL Server 2025

EF Core now supports approximate vector search when targeting SQL Server 2025, enabling efficient similarity searches in AI and machine learning applications.

JSON Mapping Fully Integrated into the Relational Model

JSON mapping is no longer experimental; it is now a first-class part of the relational model. This simplifies working with JSON columns and hybrid data structures.

Temporal Period Properties Map to CLR Properties

Developers can map temporal period properties (such as validity ranges) directly to CLR properties, making it easier to work with temporal tables in code.

dotnet ef Reads Defaults from dotnet-ef.json

The dotnet ef tool now reads configuration defaults from a dotnet-ef.json file, reducing the need for repetitive command-line arguments in team projects.

All EF Core updates are detailed in the EF Core release notes.

Getting Started with .NET 11 Preview 4

To start experimenting with .NET 11 Preview 4, download and install the .NET 11 SDK from the official site. Windows users with Visual Studio should install the latest Visual Studio 2026 Insiders for full compatibility. Alternatively, you can use Visual Studio Code with the C# Dev Kit extension. Dive in and explore the new features today!