[11.0 P6] Blazor Preview 6 coverage

[guardrex]

Addresses #37274

🚧👷‍♀️ WIP 👷‍♂️🏗️

Dan, the introductory union coverage in the Components overview article currently assigns a C#-built RenderFragment, which works 🎉 ...

<Slot Content="@renderFrag" />

@code {
    private SlotContent renderFrag;

    protected override void OnInitialized()
    {
        renderFrag = 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, they'll 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.