Exploring .NET 11 Preview 4: New Features and Enhancements Across the Ecosystem

The .NET team has unveiled Preview 4 of .NET 11, bringing a wave of improvements that touch nearly every corner of the framework. From runtime performance boosts to refreshed tooling and expanded library capabilities, this release continues to refine the developer experience. Whether you’re building web applications, mobile apps, or cloud services, the latest preview offers compelling updates. Below, we break down the key enhancements across Libraries, Runtime, SDK, C#, ASP.NET Core, .NET MAUI, and Entity Framework Core. Dive in to see what’s new and how to get started.

Libraries: Major Overhauls and New APIs

The System.IO.Compression namespace receives its most significant update in years. A new set of Deflate, ZLib, and GZip encoder/decoder APIs now operate directly on Span<byte> and ReadOnlySpan<byte>, reducing allocations and boosting throughput. Additionally, floating-point number handling gains hex formatting and parsing capabilities, making it easier to work with IEEE 754 representations.

In System.Text.Json, developers will find refined serialization options and performance improvements. For a complete list of library changes, see the official library updates.

Runtime: Faster Execution and Better Code Generation

The .NET Runtime now compiles its libraries with runtime-async, a new mode that enables asynchronous streaming and improved memory management. JIT optimizations have been applied to common patterns, and hardware intrinsics gain additional support for modern CPU instructions. Together, these changes lead to tighter code generation and faster execution in performance-critical paths.

Explore the full runtime release notes for deeper details.

SDK: Enhanced Tooling and Telemetry

The .NET SDK introduces several quality-of-life improvements:

• dotnet watch now supports device selection for .NET MAUI and mobile projects, allowing you to target a specific emulator or physical device directly from the command line.
• Fish shell completions have been added, matching the existing support for Bash, Zsh, and PowerShell.
• Commands like dotnet reference now fall back to the current directory when no path is provided, reducing friction in everyday workflows.
• OpenTelemetry replaces Application Insights as the default telemetry provider for CLI operations, aligning with industry standards.

Check out the SDK update page for more.

C#: Diagnostics and Build Performance

The C# compiler receives two notable refinements:

• Clearer diagnostics for misplaced #! shebang directives, helping you fix syntax errors more quickly in script files.
• An opt-in compilation cache for the VBCSCompiler build server, which can speed up incremental builds by reusing previously compiled results.

Visit the C# updates for the complete list.

ASP.NET Core: OpenAPI, Blazor, and MCP

This preview enriches the ASP.NET Core ecosystem with several new features:

• Generated OpenAPI documents now support the HTTP QUERY method, enabling more accurate API descriptions.
• Blazor introduces SupplyParameterFromTempData, a new attribute that simplifies passing temporary data between pages.
• Server-initiated Blazor Server circuit pause allows the server to temporarily suspend a circuit, improving resource management.
• The MCP Server (Model Context Protocol) template ships with the SDK, making it easier to build AI-integrated backends.

Read the ASP.NET Core release notes for details.

.NET MAUI: Device Watching for Android and iOS

Mobile developers get a welcome upgrade: dotnet watch now supports Android and iOS targets. This means you can hot reload your .NET MAUI app on a real device or emulator during development, accelerating the inner loop. Combined with the device selection feature in the SDK, the mobile development experience becomes more fluid.

Learn more from the .NET MAUI updates.

Entity Framework Core: Smarter Queries and Mapping

Entity Framework Core continues to evolve with database-specific and modeling improvements:

• Approximate vector search is now available for SQL Server 2025, enabling AI-powered similarity queries using vector indexes.
• JSON mapping is fully integrated into the relational model, making it seamless to store and query JSON documents.
• Temporal period properties can now map directly to CLR properties, simplifying time‑based entity tracking.
• The dotnet ef tool now reads defaults from a dotnet-ef.json configuration file, reducing repetitive command-line flags.

See the EF Core change log for the full list.

Getting Started with .NET 11 Preview 4

Ready to try the new features? Download the .NET 11 SDK and start experimenting. If you’re on Windows with Visual Studio, install the latest Visual Studio 2026 Insiders build. Alternatively, Visual Studio Code with the C# Dev Kit extension fully supports .NET 11.

This preview offers a glimpse into the direction of the .NET platform. Share your feedback and help shape the final release!