A newer way to do this in .NET Core is with TagHelpers.
https://docs.microsoft.com/en-us/aspnet/core/mvc/views/tag-helpers/intro
Building on these examples (MaxLength, Label), you can extend the existing TagHelper to suit your needs.
using Microsoft.AspNetCore.Razor.TagHelpers;
using System.ComponentModel.DataAnnotations;
using System.Collections.Generic;
using Microsoft.AspNetCore.Mvc.ViewFeatures;
using System.Linq;
namespace ProjectName.TagHelpers
{
[HtmlTargetElement("input", Attributes = "asp-for")]
public class RequiredTagHelper : TagHelper
{
public override int Order
{
get { return int.MaxValue; }
}
[HtmlAttributeName("asp-for")]
public ModelExpression For { get; set; }
public override void Process(TagHelperContext context, TagHelperOutput output)
{
base.Process(context, output);
if (context.AllAttributes["required"] == null)
{
var isRequired = For.ModelExplorer.Metadata.ValidatorMetadata.Any(a => a is RequiredAttribute);
if (isRequired)
{
var requiredAttribute = new TagHelperAttribute("required");
output.Attributes.Add(requiredAttribute);
}
}
}
}
}
You'll then need to add it to be used in your views:
@using ProjectName
@addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
@addTagHelper "*, ProjectName"
Given the following model:
using System;
using System.ComponentModel.DataAnnotations;
namespace ProjectName.Models
{
public class Foo
{
public int Id { get; set; }
[Required]
[Display(Name = "Full Name")]
public string Name { get; set; }
}
}
and view (snippet):
<label asp-for="Name"></label>
<input asp-for="Name"/>
Will result in this HTML:
<label for="Name">Full Name</label>
<input required type="text" data-val="true" data-val-required="The Full Name field is required." id="Name" name="Name" value=""/>
I hope this is helpful to anyone with same question but using .NET Core.