What's new in ASP.NET Core 6

1st November 2021

I’m compiling information for our next Adelaide .NET User Group meetup which is focusing on the launch of .NET 6 and Visual Studio 2022.

Way back in February 2021, the major themes were outlined for ASP.NET Core in .NET 6. They were:

• Hot reload: Quickly make UI and code updates to running apps without losing app state for faster and more productive developer experience.
• Micro APIs: Simplify building API endpoints with much less code and ceremony.
• Single-file publishing: Build small, standalone, high-performance apps and services.
• WebAssembly ahead-of-time (AoT) compilation: Compile .NET code in Blazor WebAssembly apps directly to WebAssembly when publishing for significantly improved runtime performance.
• Updated single-page app (SPA) support Update SPA integration in ASP.NET Core to work seamlessly with the latest modern front-end JavaScript frameworks.
• Blazor hybrid desktop apps: Combine the best of Blazor and .NET Multi-platform App UI to build cross-platform hybrid desktop apps.
• HTTP/3: Add support for HTTP/3 and QUIC in ASP.NET Core supported servers.

Each preview then went on to incrementally work towards these goals:

Preview 1

• Support for IAsyncDisposable in MVC
• DynamicComponent
• Input ElementReference exposed on relevant components
• Nullable reference type annotations

Preview 2

• Razor compiler updated to use source generators
• Support for custom event arguments in Blazor
• CSS isolation for MVC Views and Razor Pages
• Infer component generic types from ancestor components
• Preserve pre-rendered state in Blazor apps
• SignalR – Nullable annotations

Preview 3

• Smaller SignalR, Blazor Server, and MessagePack scripts
• Enable Redis profiling sessions
• HTTP/3 endpoint TLS configuration
• Initial .NET Hot Reload support
• Razor compiler no longer produces a separate Views assembly
• Shadow-copying in IIS
• Vcpkg port for SignalR C++ client
• Reduced memory footprint for idle TLS connections
• Remove slabs from the SlabMemoryPool
• BlazorWebView controls for WPF & Windows Forms

Preview 4

• Introducing minimal APIs
• Async streaming
• HTTP logging middleware
• Use Kestrel for the default launch profile in new projects
• IConnectionSocketFeature
• Improved single-page app (SPA) templates
• .NET Hot Reload updates
• Generic type constraints in Razor components
• Blazor error boundaries
• Blazor WebAssembly ahead-of-time (AOT) compilation
• .NET MAUI Blazor apps
• Other performance improvements

Preview 5

• .NET Hot Reload updates for dotnet watch
• ASP.NET Core SPA templates updated to Angular 11 and React 17
• Use Razor syntax in SVG foreignObject elements
• Specify null for Action and RenderFragment component parameters
• Reduced Blazor WebAssembly download size with runtime relinking
• Configurable buffer threshold before writing to disk in Json.NET output formatter
• Subcategories for better filtering of Kestrel logs
• Faster get and set for HTTP headers
• Configurable unconsumed incoming buffer size for IIS

Preview 6

• Improved Blazor accessibility
• Required Blazor component parameters
• Efficient byte array transfers for JavaScript interop
• Optional parameters for view component tag helpers
• Angular template updated to Angular 12
• OpenAPI support for minimal APIs
• Inject services into minimal APIs without [FromServices] attribute
• Configure the accept socket for Kestrel
• IHttpActivityFeature
• Long running activity tag for SignalR connections
• WebSocket compression
• SignalR WebSockets TestServer support
• New OnCheckSlidingExpiration event for controlling cookie renewal
• ClientCertificateMode.DelayCertificate

Preview 7

• Parity with existing experiences for minimal APIs
• Added IResult implementations for producing common HTTP responses
• Support Request, Response and User for minimal actions
• Minimal host and template improvements
• Supply Blazor component parameters from the query string
• Replace the current URI in the browser history from Blazor
• New DynamicComponent.Instance property
• Blazor streaming interop from JavaScript to .NET
• Large file upload & faster file uploads with Blazor
• Modify HTML <head> content from Blazor components
• Support for the multiple attribute on <select> elements in Blazor
• Support for HTTP/3 in Kestrel
• QUIC support moved to the shared framework
• Allow control over Activity creation
• Support for non-ASCII characters in Kestrel response headers
• Add W3CLogger
• Add authentication expiration option to SignalR

Release Candidate 1

• Render Blazor components from JavaScript
• Blazor custom elements
• Manipulate the query string from Blazor
• .NET to JavaScript streaming
• PageX and PageY in MouseEventArgs
• Blazor templates updated to set page titles
• Disabled long-polling transport for Blazor Server
• Collocate JavaScript files with pages, views, and components
• JavaScript initializers
• Customize Blazor WebAssembly packaging
• Template improvements
• Minimal API updates
• Support for Latin1 encoded request headers in HttpSysServer
• Emit KestrelServerOptions via EventSource event
• Add timestamps and PID to ASP.NET Core Module logs
• New DiagnosticSource event for rejected HTTP requests
• Create a ConnectionContext from an Accept Socket
• Streamlined HTTP/3 setup
• Upgrade to Duende Identity Server

In addition to these regular previews, two other blog posts were published that relate to ASP.NET Core 6:

• ASP.NET Core 6 and Authentication Servers - .NET 6 will have IdentityServer templates. .NET 7 options under consideration.
• HTTP/3 support in .NET 6 - HTTP/3 support is included as a preview feature in .NET 6 (partly due to the fact that the RFC for HTTP/3 has not been finalised yet)