ASP.NET Core Conditional Tag Helper Class

Question

When implementing a solution to an existing question for a helper conditional class helper in ASP.NET Core 2.0, I do not get the expected results.

The tag helper is a direct copy of a published response and has not been modified.

Following the example, instead of the class name, I get the full name of the attribute along with the specified class.

What am I doing wrong?

Taghelper

using Microsoft.AspNetCore.Razor.TagHelpers;
using System;
using System.Collections.Generic;
using System.Linq;

namespace PerformanceTools.TagHelpers
{
    [HtmlTargetElement("div", Attributes = ClassPrefix + "*")]
    public class ConditionClassTagHelper : TagHelper
    {
        private const string ClassPrefix = "condition-class-";

        [HtmlAttributeName("class")]
        public string CssClass { get; set; }

        private IDictionary<string, bool> _classValues;

        [HtmlAttributeName("", DictionaryAttributePrefix = ClassPrefix)]
        public IDictionary<string, bool> ClassValues
        {
            get
            {
                return _classValues ?? (_classValues = new Dictionary<string, bool>(StringComparer.OrdinalIgnoreCase));
            }
            set
            {
                _classValues = value;
            }
        }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            var items = _classValues.Where(e => e.Value).Select(e => e.Key).ToList();

            if (!string.IsNullOrEmpty(CssClass))
            {
                items.Insert(0, CssClass);
            }

            if (items.Any())
            {
                var classes = string.Join(" ", items.ToArray());

                output.Attributes.Add("class", classes);
            }
        }
    }
}

controller

public IActionResult ConditionalTest()
{
    List<ConditionalTestViewModel> model = new List<ConditionalTestViewModel>();
    model.Add(new ConditionalTestViewModel { Active = true });
    model.Add(new ConditionalTestViewModel { Active = false });
    return View("ConditionalTest", model);
}

Model

public class ConditionalTestViewModel
{
    public bool Active { get; set; }
}

View

@model IEnumerable<ConditionalTestViewModel>

<div>Conditional Test</div>
@foreach(var c in Model)
{
    <div condition-class-active="@c.Active">@c.Active</div>
}

Output

<div id="container-body" class="container">

<div>Conditional Test</div>
    <div condition-class-active="conditional-class-active">True</div>
    <div>False</div>
</div>

Update: As indicated, TagHelper condition-class-*not conditional-class-*, I updated my question, but the problem still remains.

Answer 1

, , . active-condition active-class-active, :

<div>Conditional Test</div>
@foreach(var c in Model)
{
    <div condition-class-active="@c.Active">@c.Active</div>
}

_ViewImports.cshtml taghelper

@addTagHelper "*, WebApplication3"