Why do anything on the 2nd call to OnInitializedAsync()?

[DavidThielen]

This is a follow-on question to my question Why is OnInitializedAsync() called twice?

What I have been doing to date, based on Microsoft's guidance that everything should be requested in the pre-render call, is:

1. Anything that might be cached I call. If it is not in the cache, the pre-render pass will read it in to the cache. Then the second pass will get it from the cache.
2. Anything small I first look for in the PersistingComponentStateSubscription. If there, I use that. If not there, I read it, save it in the persisted store, and use it.
3. For anything else, I only call it if it is not a Pre-Render call (HttpContext is not null).

But thinking about it today, it strikes me that we want to call all initialization in the pre-render pass. And then do nothing on the second pass. Which would be the following:

1. Read PersistingComponentStateSubscription. If that has a value, return.
2. Write 'true' to PersistingComponentStateSubscription
3. Perform all initialization, including reading everything needed from the DB even if that will take 10+ seconds.

Is there any downside to the above? I ask, because why have 2 passes if doing this meets the Microsoft guidance to get everything in the pre-render pass?

The flip approach to the above is to do:

1. Do all fast initialization.
2. IfPreRender, return (exit).
3. Do all slow initialization.

But following that means all the slow initialization will be started a bit later. That will mean it will take longer to fully initialize the page. And as Microsoft's guidance implies that a slow pre-render initialization will not slow down the rendering of the page skeleton, I don't see any advantage to this approach.

I'm asking the above because either approach, that seems to me to be the fastest with no duplication of DB reads, means basically that I am reducing this down to a single pass of OnInitializationAsync(), ignoring the other pass. But the Blazor team is smart and I don't think they would give us 2 passes to no advantage.

So what am I missing?

thanks - dave