Create Custom Tag Helpers in ASP.NET Core MVC

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29 Nov, 2019 Categories: ASP.NET Core MVC

Create ASP.NET Core MVC Project

On the Visual Studio, create new ASP.NET Core Web Application project

Select Empty Template

Click Ok button to Finish




Add Configurations

Open Startup.cs file and add new configurations as below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;

namespace LearnASPNETCoreMVCWithRealApps
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseStaticFiles();

            app.UseMvc(routes =>
            {
                routes.MapRoute(
                    name: "default",
                    template: "{controller=Demo}/{action=Index}/{id?}");
            });

        }
    }
}

Create Tag Helpers

Create new folder named TagHelpers. In this folder, create new custom tag helpers as below:

Hello Tag

In TagHelpers folder, create new class named HelloTag.cs as below:

using Microsoft.AspNetCore.Razor.TagHelpers;

namespace LearnASPNETCoreMVCWithRealApps.TagHelpers
{
    [HtmlTargetElement("hello", TagStructure = TagStructure.NormalOrSelfClosing)]
    public class HelloTag : TagHelper
    {
        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            output.TagName = "";
            output.Content.SetHtmlContent("<h3>Hello</h3>");
        }
    }
}




Sum Tag

In TagHelpers folder, create new class named SumTag.cs as below:

using Microsoft.AspNetCore.Razor.TagHelpers;

namespace LearnASPNETCoreMVCWithRealApps.TagHelpers
{
    [HtmlTargetElement("sum", TagStructure = TagStructure.NormalOrSelfClosing)]
    public class SumTag : TagHelper
    {
        [HtmlAttributeName("a")]
        public double a { get; set; }

        [HtmlAttributeName("b")]
        public double b { get; set; }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            output.TagName = "";
            output.Content.SetHtmlContent((a + b).ToString());
        }
    }
}

Create Razor View Imports

Right click current project and select Razor View Imports and click Add button to finish. In _ViewImports.cshtml file, add TagHelpers libraries as below:

@addTagHelper *, LearnASPNETCoreMVCWithRealApps

Create Controller

Create new folder named Controllers. In this folder, create new controller named DemoController.cs as below:

using Microsoft.AspNetCore.Mvc;

namespace LearnASPNETCoreMVCWithRealApps.Controllers
{
    [Route("demo")]
    public class DemoController : Controller
    {
        [Route("")]
        [Route("index")]
        [Route("~/")]
        public IActionResult Index()
        {
            return View();
        }
    }
}




Create View

Create new folder named Views. In this folder, create new folder named Demo. Create new view named Index.cshtml as below:

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>Custom Tag Helpers in ASP.NET Core MVC</title>
</head>
<body>

    <hello/>
    <br />
    Sum: <sum a="2" b="3" />

</body>
</html>

Structure of ASP.NET MVC Core Project




Run Application

Access Index action in Demo controller with following url: http://localhost:48982/Demo/Index

Output

Tags

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