News

.NET 11 Preview 6 Roundup: ASP.NET Core, MAUI, C#, EF Core and SDK Updates

• By David Ramel
• 07/15/2026

Microsoft has released .NET 11 Preview 6, delivering another broad collection of improvements across the company's open source, cross-platform development stack rather than one dominant headline feature.

The July 14 announcement covers the .NET runtime and libraries, software development kit (SDK), C#, ASP.NET Core, .NET Multi-platform App UI (.NET MAUI), Entity Framework Core (EF Core), F# and container images.

.NET 11 is scheduled to become generally available on Nov. 10, 2026. It will be a Standard Term Support (STS) release, receiving free Microsoft support and patches for two years, through Nov. 9, 2028.

Across the larger .NET 11 development cycle, Microsoft has described its work in terms of making the platform faster, more secure and productive while preparing it for modern cloud, cross-platform and AI-era application development. Preview 6 continues that work with performance optimizations, expanded Native Ahead-of-Time (Native AOT) support, safer web defaults and improvements to everyday coding, testing and deployment workflows.

ASP.NET Core Expands Validation, Security and Union Support
The ASP.NET Core release notes contain one of the longest lists of additions in Preview 6, including:

• Async validation for Minimal APIs: Minimal API validation now runs the new asynchronous DataAnnotations capabilities introduced in the base libraries, allowing rules to query databases or remote services without blocking a thread.
• Automatic cross-origin protection: ASP.NET Core can automatically protect cookie-authenticated endpoints from cross-site request forgery attacks involving requests from untrusted origins.
• Blazor virtualization: Blazor's Virtualize component can scroll directly to a specified item, helping applications navigate large virtualized collections.
• Server-controlled Blazor behavior: Servers gain additional control over Blazor client behavior and enhanced navigation.
• OpenAPI 3.2: ASP.NET Core now generates OpenAPI 3.2 documents by default.
• C# unions: Union types can be used as JSON request bodies and response types, while ASP.NET Core can represent union return types in generated OpenAPI documents.
• Endpoint short-circuiting: Developers can apply an attribute to endpoints that should terminate the request pipeline without invoking subsequent middleware.
• SignalR updates: Clients can refresh authentication credentials during long-running connections and cancel individual hub invocations.
• File-based apps: The dotnet user-jwts command now supports file-based C# applications.

Libraries Add Async DataAnnotations and Stream Adapters
The base-library updates include four new stream types that expose existing memory, text and segmented buffers through APIs expecting a Stream, without first copying the contents into a MemoryStream.

• ReadOnlyMemoryStream wraps a ReadOnlyMemory<byte>.
• WritableMemoryStream exposes writable Memory<byte> through a fixed-size stream.
• ReadOnlySequenceStream works over segmented ReadOnlySequence<byte> buffers, including those used with System.IO.Pipelines.
• StringStream exposes a string or character memory through a stream using a specified encoding.

DataAnnotations gains asynchronous validation through AsyncValidationAttribute, IAsyncValidatableObject and async versions of the Validator APIs. The related options infrastructure can also validate configuration asynchronously, including during application startup.

Other library changes include native System.Text.Json serialization for C# union types, rules-based configuration for Activity tracing, new vector construction and lane-rearrangement operations, and process APIs for starting Windows processes in a suspended state or looking them up without throwing when an identifier is not found.

Runtime Work Continues on Async, JIT and Native AOT
The runtime changes continue Microsoft's performance work on runtime-implemented async/await, following the suspension and resumption improvements delivered in Preview 5.

• Additional async optimizations reduce allocation and execution costs.
• Just-in-Time (JIT) compilation receives further code-generation and optimization improvements.
• Applications can write crash-report information from inside the affected process, providing additional diagnostic context.
• Native AOT interface dispatch is faster.
• Single Instruction, Multiple Data (SIMD) APIs gain additional vector lane construction and composition operations.

SDK Improves Testing, Native AOT and File-Based Apps
The SDK and command-line interface updates span Native AOT, testing, web assets, containers and file-based application development.

• Native AOT CLI: The experimental Native AOT command-line path now shares a parser with the managed CLI and understands the full command surface. Commands that can run entirely without the managed runtime execute natively, while others automatically fall back to the managed implementation.
• dotnet test: The testing command gains additional options and clearer output.
• Testing templates: Project templates support xUnit.net v3 and NUnit running on Microsoft.Testing.Platform.
• File-based apps: The #:include directive can reference compiled .dll files.
• Podman publishing: SDK container publishing supports multi-architecture images with Podman.
• TypeScript integration: TypeScript compiler output can be incorporated into ASP.NET Core Static Web Assets.
• Build infrastructure: CLI behavior now honors the MSBuild server setting and standard OpenTelemetry environment variables.

C# Adds Extension Indexers
The C# 15 work in Preview 6 adds extension indexers, expanding the extension-member capability introduced in .NET 10.

Developers can define this[...] access for an existing type inside an extension block, alongside extension methods and properties. One example is adding from-the-end Index-based access to IReadOnlyList<T> without modifying the interface itself.

The preview also moves the supporting types required by the developing C# union feature into the standard .NET libraries, rather than requiring separate compiler-provided support. Union declarations and their associated rules remain preview features subject to change before general availability.

.NET MAUI Modernizes CollectionView and Shell
The .NET MAUI updates continue Microsoft's effort to move the cross-platform framework away from legacy Xamarin.Forms-era implementations.

• CollectionView2 on Windows: The next-generation CollectionView gains a Windows handler based on WinUI's ItemsRepeater, joining existing implementations for Android, iOS and Mac Catalyst.
• Android Shell: Shell adopts a handler-based architecture on Android.
• Compatibility cleanup: The legacy Microsoft.Maui.Controls.Compatibility package has been removed.
• HybridWebView: The control is now compatible with Native AOT and trimming.
• Geolocation: Applications can specify a minimum distance that a device must move before receiving another location update.
• MediaPicker: Android applications can recover media-picker results after the operating system terminates and later restores the app process.
• Apple tooling: Apple workloads move to stable Xcode 26.6 support.

The release also includes another broad reliability and platform-fix wave across controls, layout, navigation, gestures and the Android and Apple workloads.

EF Core Expands LINQ Translation and Complex-Type Modeling
The EF Core Preview 6 work includes several changes intended to produce more capable or efficient database queries.

• Queryable.FullJoin can be translated to a SQL FULL OUTER JOIN.
• Conditional expressions can be simplified into SQL NULLIF.
• Redundant null-propagation checks are removed from generated SQL.
• List<T>.Exists can be translated into an SQL EXISTS subquery.
• Additional TimeOnly, string.Join and string.Concat scenarios are translated for SQLite.
• Keys and indexes can reference properties nested inside complex types.
• SQL Server indexes can be defined over properties stored inside JSON-mapped columns.
• A new API supports relationships that exist in the object model but are not enforced by a database foreign-key constraint.

Other work covers Azure Cosmos DB provider behavior, migrations and a dependency change for Microsoft.Data.Sqlite.

F# and Container Image Updates
The F# changes include inlining for Array.init initialization lambdas, parser improvements for interpolated strings next to equals signs, cleaner output from F# Interactive's --quiet mode, new signature-file diagnostics and more accurate sequence points for debugging.

The container image updates move .NET 11's Azure Linux images from Azure Linux 3.0 to an Azure Linux 4.0 beta. Microsoft also reduced Native AOT SDK image sizes by using GCC instead of Clang/LLVM and installing only required compilation packages.

The reported reductions range from 15.6 percent for Ubuntu Resolute to 32.7 percent for Azure Linux, with the Alpine image shrinking by 123.9 MB, or 30.9 percent.

Getting Started
Developers can download and install the .NET 11 Preview 6 SDK. Microsoft recommends the latest Visual Studio 2026 Insiders release for Windows developers using Visual Studio.

Visual Studio Code users can work with the preview through Microsoft's C# Dev Kit extension.