MVC6 (ASP.NET5) 自定义TagHelper

1) 在 _ViewImports.cshtml 中引入TagHelper类所在的 Assembly . (注意不是namespace)  :

@addTagHelper "*, WebApplication1"

2) 创建TagHelper类：

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Razor.Runtime.TagHelpers;
 using Microsoft.AspNet.Razor.TagHelpers;

 namespace WebApplication1.TagHelpers
 {
     // You may need to install the Microsoft.AspNet.Razor.Runtime package into your project
     [HtmlTargetElement("field")]
     public class FieldTagHelper : TagHelper
     {
         [HtmlAttributeName("label")]
         public string Label { get; set; }

         [HtmlAttributeName("cols")]
         public int ColumnCount { get; set; }

         public override async Task ProcessAsync(TagHelperContext context, TagHelperOutput output)
         {
             output.TagName = "div";
             output.Attributes.Add("class", "form-group");

             var childContent = await output.GetChildContentAsync();

             output.Content.SetHtmlContent($@"
 <label class='col-md-{ColumnCount} control-label'>{Label}</label>
 <div class='form-value col-md-{12 - ColumnCount}'>{childContent.GetContent()}</div>");
         }
     }
 }

3）使用自定义Tag：

 <field label="Test Label" cols="4">
     <input asp-for="TestName" class="form-control" />
 </field>