it fixes the issue It is indeed just a case of Razor being so new. No doubt preview will work with Razor in a future version (who knows, perhaps a service pack to 2010 will add this). However, as @marcind points out, this is speculation on my side...
I wish this helpful for you I stumbled onto an issue on the AspNetCore repository and it turns out this is a tooling issue. Unfortunately, it seems to be low in the priority list even though it can be a detrimental problem. Anyway, the OP of the issue gave me an idea, which was to delete the folder with the published cshtml files and then recycle the apppool to for rediscovery of the compiled views.
How to disable html angular attribute suggestions in Visual Studio 2019?
To fix the issue you can do Step 1: Save a backup copy of C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\IDE\Extensions\Microsoft\Web Tools\Languages\Schemas\HTML\SchemaCatalog.xml (just in case) Step 2: Edit the above file to delete the following element: