The latest release of .NET 8 Preview 6 brings significant additions and changes to ASP.NET Core. The most notable enhancements for this release of ASP.NET Core are related to the Blazor alongside the updates regarding the debugging experience, testing metrics, API authoring, servers, middleware and many more.
Regarding the Blazor, several new features have been introduced to enhance its server-side rendering mode. One notable addition is the ability to model bind and validate HTTP form post values. This can be achieved by applying the SupplyParameterFromForm attribute to a component property, enabling easier data binding from form requests.
Moreover, Blazor now offers enhanced page navigation and form-handling capabilities. By intercepting requests and applying the response to the existing DOM, the framework preserves as much of the page as possible, resulting in a smoother user experience to a single-page app (SPA) while still utilizing server-side rendering.
Blazor's streaming rendering has been enhanced to preserve existing DOM elements during updates, leading to faster and smoother interactions. Developers now have the ability to specify the render mode for a component instance using the @rendermode directive attribute, granting more precise control over rendering behaviour. Enabling call site @rendermode usage requires setting the Razor Language Version to 8.0 in the project file, though this step will be automated in future framework releases, eliminating the need for manual adjustments.
Blazor WebAssembly now supports interactive rendering of components, although this option is not yet exposed in the Blazor Web App template. Interested developers can enable this functionality manually to take advantage of the interactive rendering capabilities offered by Blazor WebAssembly. A demo sample is provided to illustrate the setup of WebAssembly-based interactivity for a Counter component rendered within the Index page. This sample serves as a practical example of implementing interactivity using WebAssembly in Blazor applications.
There were a couple of improvements to how Blazor sections interact with other Blazor features. These enhancements include changes to how cascading values are handled, with values now flowing into section content from their point of definition rather than where they are rendered in a section outlet. Additionally, unhandled exceptions are now handled by error boundaries around the section content, rather than the section outlet. Furthermore, the decision on whether section content should use streaming rendering is now determined by the component where the section content is defined, rather than the component defining the section outlet.
Other significant Blazor-related changes include the introduction of cascading query string values to Blazor components, the incorporation of a Blazor Web App template option for enabling server interactivity, and template consolidation.
From Preview 6 developers can now benefit from improved testing of metrics in their applications. The introduction of ASP.NET Core metrics in a previous .NET 8 preview has made it easier to test metrics, thanks to the IMeterFactory API. This API integrates metrics with dependency injection, simplifying the process of isolating and collecting metrics for testing purposes. Whether conducting unit tests or running multiple tests simultaneously, developers can rely on IMeterFactory to gather accurate data specifically tailored to their testing needs.
ASP.NET Core reinforces its commitment to metrics support with the introduction of new, improved, and renamed counters. These enhancements aim to enhance observability in reporting dashboards and enable custom alerts for ASP.NET Core applications. The new counters include metrics for routing success and failure, exception handling, unhandled requests, and rate limiting. Improved counters now provide additional details on connection duration and transport types
Other notable changes included in this release are related to complex form binding support in minimal APIs, HTTP.sys kernel response buffering, Redis-based output caching and improved debugging experience for the Web Application type. The team recommends the installation of the latest Visual Studio 2022 Preview and there is also a full list of breaking changes in ASP.NET Core for .NET 8 so developers can check that out along the way.
Lastly, the comment section on the original release blog post has been full of reactions, regarding the changes and improvements for Blazor and the blog post has generated significant activity, with users engaging in numerous questions and discussions with the development team. To get a comprehensive understanding of the various perspectives, it is highly recommended for users explore the comment section and engage in the ongoing discussion.