自定义标签助手不起作用

Question

我正在尝试实现一个我发现的here的自定义标签帮助程序，但是它不应用active CSS类。如果我在ActiveRouteTagHelper.cs内部的任何函数中放置断点，则不会命中它们。我在这里想念一些简单的东西吗？

ActiveRouteTagHelper.cs

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using Microsoft.AspNetCore.Razor.TagHelpers;
using System;
using System.Collections.Generic;
using System.Linq;

namespace NotificationSystem.Web.Helpers
{
    [HtmlTargetElement(Attributes = "is-active-route")]
    public class ActiveRouteTagHelper : TagHelper
    {
        private readonly IHttpContextAccessor _contextAccessor;

        public ActiveRouteTagHelper(IHttpContextAccessor contextAccessor)
        {
            _contextAccessor = contextAccessor;
        }

        private IDictionary<string, string> _routeValues;

        /// <summary>The name of the action method.</summary>
        /// <remarks>Must be <c>null</c> if <see cref="P:Microsoft.AspNetCore.Mvc.TagHelpers.AnchorTagHelper.Route" /> is non-<c>null</c>.</remarks>
        [HtmlAttributeName("asp-action")]
        public string Action { get; set; }

        /// <summary>The name of the controller.</summary>
        /// <remarks>Must be <c>null</c> if <see cref="P:Microsoft.AspNetCore.Mvc.TagHelpers.AnchorTagHelper.Route" /> is non-<c>null</c>.</remarks>
        [HtmlAttributeName("asp-controller")]
        public string Controller { get; set; }

        [HtmlAttributeName("asp-page")]
        public string Page { get; set; }

        /// <summary>Additional parameters for the route.</summary>
        [HtmlAttributeName("asp-all-route-data", DictionaryAttributePrefix = "asp-route-")]
        public IDictionary<string, string> RouteValues
        {
            get
            {
                if (_routeValues == null)
                    _routeValues = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
                return _routeValues;
            }
            set
            {
                _routeValues = value;
            }
        }

        /// <summary>
        /// Gets or sets the <see cref="T:Microsoft.AspNetCore.Mvc.Rendering.ViewContext" /> for the current request.
        /// </summary>
        [HtmlAttributeNotBound]
        [ViewContext]
        public ViewContext ViewContext { get; set; }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            base.Process(context, output);

            if (ShouldBeActive())
            {
                MakeActive(output);
            }

            output.Attributes.RemoveAll("is-active-route");
        }

        private bool ShouldBeActive()
        {
            string currentController = string.Empty;
            string currentAction = string.Empty;

            if (ViewContext.RouteData.Values["Controller"] != null)
            {
                currentController = ViewContext.RouteData.Values["Controller"].ToString();
            }

            if (ViewContext.RouteData.Values["Action"] != null)
            {
                currentAction = ViewContext.RouteData.Values["Action"].ToString();
            }

            if (Controller != null)
            {
                if (!string.IsNullOrWhiteSpace(Controller) && Controller.ToLower() != currentController.ToLower())
                {
                    return false;
                }

                if (!string.IsNullOrWhiteSpace(Action) && Action.ToLower() != currentAction.ToLower())
                {
                    return false;
                }
            }

            if (Page != null)
            {
                if (!string.IsNullOrWhiteSpace(Page) && Page.ToLower() != _contextAccessor.HttpContext.Request.Path.Value.ToLower())
                {
                    return false;
                }
            }

            foreach (KeyValuePair<string, string> routeValue in RouteValues)
            {
                if (!ViewContext.RouteData.Values.ContainsKey(routeValue.Key) ||
                    ViewContext.RouteData.Values[routeValue.Key].ToString() != routeValue.Value)
                {
                    return false;
                }
            }

            return true;
        }

        private void MakeActive(TagHelperOutput output)
        {
            var classAttr = output.Attributes.FirstOrDefault(a => a.Name == "class");
            if (classAttr == null)
            {
                classAttr = new TagHelperAttribute("class", "active");
                output.Attributes.Add(classAttr);
            }
            else if (classAttr.Value == null || classAttr.Value.ToString().IndexOf("active") < 0)
            {
                output.Attributes.SetAttribute("class", classAttr.Value == null
                    ? "active"
                    : classAttr.Value.ToString() + " active");
            }
        }
    }
}

_ViewImports.cshtml

@using Web
@using Web.Models
@using Kendo.Mvc.UI
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@addTagHelper *, Kendo.Mvc
@addTagHelper *, NotificationSystem.Web.Helpers

_Layout.cshtml

...
<li class="nav-main-item" is-active-route asp-controller="Dashboard" asp-action="Index">
                        <a class="nav-main-link" asp-controller="Dashboard" asp-action="Index">
                            <i class="nav-main-link-icon fas fa-home"></i>
                            <span class="nav-main-link-name">Dashboard</span>
                        </a>
                    </li>
...