Use net8.0 for Maui tests until Maui is ready for net9.0

[LoopedBard3]

Use 8.0 channel and net8.0 dotnet version link for Maui tests until Maui is ready for net9.0. This fixes the ci_setup.py error: RuntimeError: Unable to determine the .NET SDK used for net9.0

Test run: https://dev.azure.com/dnceng/internal/_build/results?buildId=2299328&view=results

Note: The default maui blazor app has also updated, breaking those builds. Will fix in another PR, this PR fixes the ci_setup issue.
@kotlarmilos @jonathanpeppers, do either of you know the current best contact for the performance of the maui-blazor app? The new default is going to impact the results of the performance testing and require a new insertion point for when we call activity.ReportFullyDrawn(), etc.

[kotlarmilos]

In the App.cs file, the main page is created, which may be useful for measuring startup performance.

public App()
{
	InitializeComponent();

	MainPage = new MainPage();

	// Startup event
	var activity = MainActivity.Context as Activity;
	activity.ReportFullyDrawn();
}

[jonathanpeppers]

If you want to all ReportFullyDrawn(), you could call it from the Android activity class:

https://github.com/dotnet/maui/blob/main/src/Templates/src/templates/maui-blazor/Platforms/Android/MainActivity.cs

Something like OnResume() would be a decent place to call it for a plain MAUI app.

But for a MAUI+Blazor app, you want to call it after all HTML content has fully loaded?

[LoopedBard3]

Yea, after the html is all loaded is the goal. Before we were calling the report fully drawn in "protected override void OnAfterRender(bool firstRender)", is there a good way to figure out if this is still available? It used to be put in the file "app/Pages/Index.razor.cs".

[jonathanpeppers]

@Eilon @mkArtakMSFT did the OnAfterRender() method for MAUI+Blazor go away in .NET 8? Is there an alternate now?

[LoopedBard3]

I did some testing and think I found where to move the OnAfterRender(). I am working on trying to fix some other pipeline things before pushing here.

[LoopedBard3]

Test run: https://dev.azure.com/dnceng/internal/_build/results?buildId=2300319&view=results

[Eilon]

@Eilon @mkArtakMSFT did the OnAfterRender() method for MAUI+Blazor go away in .NET 8? Is there an alternate now?

Still there: https://github.com/dotnet/aspnetcore/blob/main/src/Components/Components/src/ComponentBase.cs#L144-L146

[jonathanpeppers]

So, this broke because we reworked the template?

dotnet/maui#17946

@Eilon do you think these files would move around often?

@LoopedBard3 could this error immediately if this file goes missing?

[LoopedBard3]

Yes, the template app changed along with the file structure. If there is another major change, we should see a similar build error if the Home.razor file is removed or renamed.

[Eilon]

@Eilon do you think these files would move around often?

No, this was the big template update for .NET 8, and no plans to make any significant changes until GA.