Why is IntelliSense picked up when opening an asp.net mvc site in Visual Studio, but not when opening an asp.net core site?

Question

ASP.NET

Why is IntelliSense picked up when opening an asp.net mvc site in Visual Studio, but not when opening an asp.net core site?
In the first case, auto-substitution of classes, properties and methods is connected, and in the second, everything glows with errors

The name 'xxx' does not exist in the current context

And he also swears at the missing an assembly reference, and for some reason he is looking for System.Web, although, it seems, just one of the Core bonuses was to get rid of System.Web.

I understand that editing sites on asp.net in RuntimeCompilation mode is not a must, but, nevertheless, what could be the reason (and is it generally treated)?

Answer 1

You probably don't have the .net core sdk installed, or you open it in some strange way.

Answer 2

Without js - sending the form to the same address.
With js - location.reload()

Answer 3

Without JS: Write A in the
head
to send the correct headers to the server, and until the page is refreshed, send HTTP 304
With JS:
As long as your imagination is enough, you can poll the server with a timer / interval and as soon as it becomes necessary to refresh the page, on websockets implement the solution, then as soon as the server issues an update command, execute it, etc.