Tag Helper : required-claims

RequiredClaimsTagHelper.cs

using System.Linq;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Razor.TagHelpers;

namespace Infrastructure.MVC
{
	[HtmlTargetElement(Attributes = "required-claim")]
	public class RequiredClaimsTagHelper : TagHelper
    {
		private readonly IHttpContextAccessor httpContextAccessor;

		public RequiredClaimsTagHelper(IHttpContextAccessor httpContextAccessor)
		{
			this.httpContextAccessor = httpContextAccessor;
		}

		[HtmlAttributeName("required-claim")]
		public string RequiredClaim { get; set; }

		public override void Process(TagHelperContext context, TagHelperOutput output)
		{
			if (null == httpContextAccessor.HttpContext.User.Claims.FirstOrDefault(claim => claim.Type == this.RequiredClaim))
			{
				output.SuppressOutput();
			}
		}
	}
}

Use it on any html element to hide it if current user does not have required claim

<a required-claim="admin" asp-controller="Home" asp-action="About">About</a>

Concerns

1. Claim value is not checked, it can be even empty
2. User.Identity.IsAuthenticated is not checked since it is orthogonal concept to claims - claim existence is not dependant on Authentication