I followed a few guides on creating a custom tag helper for ASP Core.
This is my helper:
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.Asp
So I wasted a bit of time chasing the problem where a taghelper was not working. After a while I went to bed and today with fresh eyes I gave it another try, was then that I realized that I did not add the @addTagHelper in the Razor Pages folder only in the Views folder.
So if you like I have this /Pages + /Views concepts make sure to go through all those _ViewImports.cshtml. Leaving this note here hopefully will remind someelse's tired brain, and if it helped take a break and go for a walk or a snooze.