Better dev. experience when `AddServerRenderMode` or `AddWebAssemblyRenderMode` is missing

[danroth27]

I'm trying to upgrade a Blazor Server app to .NET 8 using the new full stack web UI model. I've setup the Blazor Router component to render using the server interactive render mode, but the rendered pages (like the counter) don't render interactively.

Repro steps:

• Install .NET 8 Preview 6
• Clone https://github.com/danroth27/Net8BlazorServer
• Build and run the app
• Try out the counter

Expected result: The counter works
Actual result: The counter doesn't increment when clicked

[danroth27]

@SteveSandersonMS Is this really the same issue as #49303?

[SteveSandersonMS]

@danroth27 The issue is that the MapRazorComponents middleware doesn't realise you're using Server rendermode (because it only sees [RenderModeServer], not @rendermode="Server") and hence doesn't enable the endpoints for server. Two possible workarounds:

1. Tell it explicitly. In Program.cs, update MapRazorComponents to add AddServerRenderMode. That is, line 29 becomes app.MapRazorComponents<Host>().AddServerRenderMode();
2. Or, change App.razor to contain @attribute [RenderModeServer] instead of using callsite rendermode for that component.

@javiercn Now we support callsite rendermodes we can't rely on statically detecting rendermodes. Do you have a preference on how to handle this? I'd recommend we change the source generator not to try doing static detection since that can't be reliable, and instead register the endpoints:

• By default based on which DI services were configured. For example, if you have AddServerComponents then we should behave as if you also have AddServerRenderMode by default.
• (Optional) ... and if people really want to override this for different branches in the middleware pipeline, let them. For example we could allow something like app.MapRazorComponents<Host>().ClearRenderModes().AddServerRenderMode(); so the DI services can be ignored. This will be a very niche edge case though so I think it would be fine if we didn't have this initially in NET 8.

What do you think?

[AmarjeetBanwait]

Well adding .AddServerRenderMode(); and removing @attribute [RenderModeServer] from Counter.razor makes routing intractive. But button on Counter.razor stops working.

FetchData.razor page is also intractively loading but Removing @attribute [StreamRendering(true)] Loading... section doesn't show up page doesn't change content untill OnInitializedAsync finishes.

Adding @attribute [RenderModeServer] in counter.razor breaks intractive routing but now counter button works and app fallbacks to full page refresh.

Also ToggleNavMenu button doesn't work without adding @attribute [RenderModeServer] in NavMenu.razor but again this will break intractive routing.

[Dulatr]

Commented in a different issue that was closed out for updates coming in Preview 7, but to @AmarjeetBanwait's comment I'm not able to get interactivity working any combination of those. Is there a current working sample I can view that demonstrates the interactivity in Preview 6?

[danroth27]

@Dulatr Did you try creating a Blazor Web App using the new template and selecting the "Use interactive server components" option? That should enable interactivity for the Counter component. If you want to see how to enable interactivity for the entire app using Blazor Server see https://github.com/danroth27/Net8BlazorServer.

[Dulatr]

@danroth27 Thank you for that. Your repo provided solved my problem exactly. A combination of the <RazorLangVersion>8.0</RazorLangVersion> workaround, the migration of the _Host.cshtml to the Host.razor, and the differences in the program file fixed it for me. Enabling interactivity for the entire app suits the need of our test project. I feel a bit silly missing a lot of that in the original posting.