[11.0 P6] Blazor Preview 6 coverage

[guardrex]

Addresses #37274

🚧👷‍♀️ WIP 👷‍♂️🏗️ ... Only C# unions at this point.

Dan ... Prelim remarks and then a question on the introductory union coverage in the Components overview article ...

Prelim

• You requested something short, leaving detail to the C# reference, but I'd like to pitch examples that appeal to my inclination to provide a fully working, cut-'n-paste examples that cover a couple of bases, namely ...

  • A C# switched RenderFragment for rendering.
  • An inline Razor syntax switched SlotContent approach for rendering.

  I'll shorten the examples to your liking.

• The DynamicComponent presentation explains out the boxing requirement with a fully (not 😄) working unboxed case before presenting the correct coding approach. Overkill? Maybe. Let me know if you want that to only show the working approach with merely a passing remark on the boxing requirement.

• The links used earlier were to the What's New content on unions; but for reference content, we should link the C# reference, which is available now ...

  https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/union

  I leave the What's New link in our What's New coverage (and I place Bill's blog link temporarily in the reference content), but I add the C# reference link to that coverage on this PR. BTW ... that C# What's New link is pointing to the wrong page. It was going to C# 14 content, but I fix that here, too.

❓ Question ❓

Currently, the Components overview article example assigns a C#-built RenderFragment, which works 🎉 ...

<Slot Content="@content" />

@code {
    private SlotContent content;

    protected override void OnInitialized()
    {
        content = new SlotContent((RenderFragment)(b =>
        {
            ...
        }));
    }

...
}

However, I was expecting (hoping for) a Razor markup approach to work ...

<Slot>
    <button @onclick="Increment">@currentCount</button>
</Slot>

... but I couldn't get that to work (even if I named the SlotContent type in the Slot component to "ChildContent").

If there's a Razor markup way to pass that SlotContent, I think we should show it. If it can't be done, then perhaps we should warn devs off of trying it. Otherwise, some folks will probably waste a lot of time trying to get it to work.

---

Internal previews

📄 File	🔗 Preview link
aspnetcore/blazor/components/dynamiccomponent.md	aspnetcore/blazor/components/dynamiccomponent
aspnetcore/blazor/components/index.md	aspnetcore/blazor/components/index
aspnetcore/blazor/fundamentals/navigation.md	aspnetcore/blazor/fundamentals/navigation
aspnetcore/blazor/fundamentals/routing.md	aspnetcore/blazor/fundamentals/routing
aspnetcore/blazor/javascript-interoperability/call-dotnet-from-javascript.md	aspnetcore/blazor/javascript-interoperability/call-dotnet-from-javascript
aspnetcore/blazor/javascript-interoperability/call-javascript-from-dotnet.md	aspnetcore/blazor/javascript-interoperability/call-javascript-from-dotnet
aspnetcore/blazor/state-management/prerendered-state-persistence.md	aspnetcore/blazor/state-management/prerendered-state-persistence
aspnetcore/mvc/models/model-binding.md	aspnetcore/mvc/models/model-binding
aspnetcore/signalr/hubs.md	aspnetcore/signalr/hubs

[Copilot]

Pull request overview

Updates ASP.NET Core documentation for .NET 11 Preview 6, focusing on C# union types coverage across Blazor, SignalR, MVC, and Minimal APIs, and aligning union-type links with current C# reference material.

Changes:

• Update several union-type references to point to the C# union type language reference.
• Add/expand Blazor guidance for union types (component parameters, DynamicComponent boxing, JS interop support note, and a PCS/serialization caveat).
• Refresh article metadata dates where substantial content was added/updated.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
aspnetcore/signalr/hubs.md	Updates the union types link used in the SignalR JsonHubProtocol note.
aspnetcore/release-notes/aspnetcore-11/includes/csharp-unions-preview-6.md	Adds a language-reference cross-link for union types in the .NET 11 Preview 6 release notes include.
aspnetcore/mvc/models/model-binding.md	Updates union types link in the model-binding note about [FromBody] support.
aspnetcore/fundamentals/minimal-apis/includes/parameter-binding8-10.md	Updates union types link in Minimal API parameter binding note.
aspnetcore/blazor/state-management/prerendered-state-persistence.md	Adds a .NET 11 note about JsonSerializerContext not flowing into union deserialization; updates metadata date.
aspnetcore/blazor/javascript-interoperability/call-javascript-from-dotnet.md	Adds a .NET 11 note that union types are supported; updates metadata date.
aspnetcore/blazor/javascript-interoperability/call-dotnet-from-javascript.md	Adds a .NET 11 note that union types are supported; updates metadata date.
aspnetcore/blazor/fundamentals/routing.md	Updates union types link in the note about route parameters not supporting unions.
aspnetcore/blazor/fundamentals/navigation.md	Updates union types link in the note about [SupplyParameterFromQuery]/[SupplyParameterFromForm] not supporting unions.
aspnetcore/blazor/components/index.md	Adds union-typed component parameter guidance + examples and updates metadata (including ai-usage).
aspnetcore/blazor/components/dynamiccomponent.md	Adds guidance and examples for boxing union-typed parameters passed via DynamicComponent dictionaries; updates metadata date.

[wadepickett]

@guardrex, just a heads up I will be unavailable from 7/10 Friday (tomorrow), all through next week until 7/21. So look to @tdykstra for any reviews you need here or on the samples repo, etc. @tdykstra is also handling the What's New. I'll start a draft today but he will be responsible for updates to keep in sync with any release note updates.

[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 6 comments.