Use Razor Tag helpers inside custom tag helper

Question

Hello this is my tag helper

    [HtmlTargetElement("card")]
    public class CardTagHelper : TagHelper
    {
        public string Title { get; set; }
        public string Icon { get; set; }
        public string Url { get; set; }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            output.TagName = "CardTagHelper";
            output.TagMode = TagMode.StartTagAndEndTag;

            var preContent = new StringBuilder();
            preContent.AppendFormat($@"
                    <div class='card custom-card'>
                        <div class='card-header'>
                            <div class='card-title'>");

            if (Url != null)
            {
                preContent.AppendFormat($@"
                                <a asp-for='{Url}'>
                                    <div class='float-left return'>
                                        <i class='fas fa-arrow-alt-circle-left fa-lg'></i>
                                    </div>
                                </a>");
            }

preContent.AppendFormat($@"<i class='{Icon}'></i>
                                {Title}
                            </div>
                        </div>
                        <div class='card-body'>");

            var postContent = new StringBuilder();
            postContent.AppendFormat($@"                                   
                        </div>
                        <div class='card-footer'>
                        </div>
                    </div>");

            output.PreContent.SetHtmlContent(preContent.ToString());
            output.PostContent.SetHtmlContent(postContent.ToString());
        }
    }
}

the output is a bootstrap 4 card

<card title="myTitle" icon="myIcon" url="redirectUrl">

    // Content here

</card>

my problem is that i would like to use asp-page instead of href on the conditional rendered string for the anchor but when i added it, it had no effect or any clickable.

EDIT

These are my viewimports, as suggested i tried include my custom helper before the Asp.Net Core

@using MyProject
@namespace MyProject.Pages
@addTagHelper *, MyProject
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers

Answer 1

However, I didn't find any article where it is explained how we can use Razor Tag helpers inside our custom tag helpers. but for my solution, i had to use actual 'href' tag instead of 'asp-for' razor tag helper like below.

    public string Url { get; set; }

    public override void Process(TagHelperContext context, TagHelperOutput output)
    {
        var content = $@"<a class='nav-link text-dark' href='/{Url}'>{Title}</a>";
        output.TagName = "li";
        output.Content.SetHtmlContent(content);
        output.Attributes.Add("class", "nav-item");
    }

Razor tag helper did behave the same it is doing for you, @Jackal. HTML generated like below -

<li class="nav-item"><a class="nav-link text-dark" href="/Index">Home</a></li>
<li class="nav-item"><a class="nav-link text-dark" href="/Restaurants/List">Restaurants</a></li>

Hope, it helps. Thanks