Update transient services guidance

[guardrex]

Fixes #31689
Addresses #28161

Blazor samples were updated on dotnet/blazor-samples#181.

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aspnetcore/blazor/fundamentals/dependency-injection.md	ASP.NET Core Blazor dependency injection

[MackinnonBuck]

Looks good, just a question about the guidance for using scoped services with server interactivity.

[hakenr]

@guardrex @MackinnonBuck I'd recommend adding one or two sentences explaining why transient disposables are a problem and why it's important to avoid them.

[guardrex]

Already done ... it's in the first (earlier) section on OwningComponentBase. These "detector" sections are just detection for those who feel that devs might add transient services in the future for some reason or perhaps have a lib add them inadvertently (although I didn't explicitly call libs out).

https://learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/dependency-injection?view=aspnetcore-8.0#utility-base-component-classes-to-manage-a-di-scope

[hakenr]

@guardrex Not sure if you're referring to this section?

In ASP.NET Core apps, scoped services are typically tied to the current request. Once the request is completed, any scoped or transient services are disposed of by the DI system. On the server side, the request scope lasts for the duration of the client connection, potentially causing transient and scoped services to live much longer than anticipated. On the client side, services registered with a scoped lifetime behave as singletons, meaning they persist longer than scoped services in typical ASP.NET Core applications.

I've discussed this with several colleagues, and despite their current knowledge and after going through this section of the documentation, they're unsure why transient disposables are particularly problematic, mainly because they haven't been following the Blazor issue tracking and haven't had the chance to look into any related issues:

• Blazor Wasm Transient Disposable registrations of AuthorizationMessageHandler aspnetcore#43234
• Make ServiceScope track list of IDisposable as WeakReference aspnetcore#2336
• Design for solving transient disposables on Blazor Server aspnetcore#26676

(Just an observation from the field, you might have different view.)

[guardrex]

I'll raise that with Mackinnon on the new PR.

[guardrex]

Ok ... it's live now ...

These updates went in yesterday. I guess I agreed with you! 😆 ... because I did make quite an update to the lead-in bits.

In spite of this PR being closed, take a look at it now here and let me know if you still have concerns about it. We'll avoid opening yet another issue in a SEA of Blazor issues at the moment 😩. I'm working fast to get the backlog down because we're starting to document .NET 9 NOW 😅.

https://learn.microsoft.com/en-us/aspnet/core/blazor/fundamentals/dependency-injection?view=aspnetcore-8.0#utility-base-component-classes-to-manage-a-di-scope

[hakenr]

It's much clearer now, but it still doesn't explain why specifically transient disposables are problematic. (The introduction mentions transient services in general, which might leave readers questioning why disposable services, in particular, should be identified as an issue.)

[guardrex]

I think the "disposables" part could be dropped. I'll open an issue to discuss this subject further with Mackinnon.