How can I pass string value for "asp-for" in asp net 5

Ok, I managed to get this working. DISCLAIMER: It is super hacky and I have no idea if I've done it in the best way possible. All I know is that it does what you want and it might point you in the right direction.

Firstly, I created a model:

using System.ComponentModel.DataAnnotations;

namespace WebApplication1.Models
{
    public class TestModel
    {
        [Required]
        public string Name { get; set; }

        [Required]
        [EmailAddress]
        [Display(Name = "Email Address")]
        public string Email { get; set; }
    }
}

Then, I made a custom tag helper. This is the horrible bit where the "magic" happens. Specifically the first section of the Process method...

using Microsoft.AspNet.Mvc.Rendering;
using Microsoft.AspNet.Mvc.ViewFeatures;
using Microsoft.AspNet.Razor.TagHelpers;
using System.Linq;

namespace WebApplication1.TagHelpers
{
    [HtmlTargetElement("edit")]
    public class EditTagHelper : TagHelper
    {
        [HtmlAttributeName("asp-for")]
        public ModelExpression aspFor { get; set; }

        [ViewContext]
        [HtmlAttributeNotBound]
        public ViewContext ViewContext { get; set; }

        protected IHtmlGenerator _generator { get; set; }

        public EditTagHelper(IHtmlGenerator generator)
        {
            _generator = generator;
        }

        public override void Process(TagHelperContext context, TagHelperOutput output)
        {
            var propName = aspFor.ModelExplorer.Model.ToString();
            var modelExProp = aspFor.ModelExplorer.Container.Properties.Single(x => x.Metadata.PropertyName.Equals(propName));
            var propValue = modelExProp.Model;
            var propEditFormatString = modelExProp.Metadata.EditFormatString;

            var label = _generator.GenerateLabel(ViewContext, aspFor.ModelExplorer,
                propName, propName, new { @class = "col-md-2 control-label", @type = "email" });

            var input = _generator.GenerateTextBox(ViewContext, aspFor.ModelExplorer,
                propName, propValue, propEditFormatString, new { @class = "form-control" });

            var validation = _generator.GenerateValidationMessage(ViewContext, aspFor.ModelExplorer, 
                propName, string.Empty, string.Empty, new { @class = "text-danger" });

            var inputParent = new TagBuilder("div");
            inputParent.AddCssClass("col-md-10");
            inputParent.InnerHtml.Append(input);
            inputParent.InnerHtml.Append(validation);

            var parent = new TagBuilder("div");
            parent.AddCssClass("form-group");
            parent.InnerHtml.Append(label);
            parent.InnerHtml.Append(inputParent);

            output.Content.SetContent(parent);
            base.Process(context, output);
        }
    }
}

NB: To make the custom TagHelper work, you need to add a line into the _ViewImports.cshtml file, like this (replace WebApplication1 with your namespace):

@addTagHelper "*, WebApplication1"

I changed my action to this, to sort of match yours (maybe you can use reflection to get your model property names here?):

public IActionResult Index()
{
    var propertyNames = new List<string>()
    {
        "Name",
        "Email"
    };
    ViewData["PropertyList"] = propertyNames;

    var m = new TestModel()
    {
        Name = "huoshan12345",
        Email = "[email protected]"
    };
    return View(m);
}

Then finally, in the view, you can do something like this:

<div class="row">
    @using (Html.BeginForm())
    {
        var propertyNames = (List<string>)ViewData["PropertyList"];
        foreach (string item in propertyNames)
        {
            <edit asp-for="@item"></edit>
        }
        <input type="submit" value="Submit" />
    }
</div>