隐式Model Binder无法在MVC中工作？

Question

I am creating a simple blog. When the User add a comment to a specific Entry that Comment details is not bind when the post request is issued ?

And when i throw a breakpoint and the post method All the parameter having a "Red Cross Sign" and stating that "Implicit function evaluation is turned off by the User" .

Here is all the Code.

Controller

using Blog.Models;
using Blog.ViewModels;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Data.Entity;

namespace Blog.Controllers
{
    public class CommentsController : Controller
    {
        private ApplicationDbContext _context;
        public CommentsController()
        {
            _context = new ApplicationDbContext();
        }

        // GET: Comments
        public ActionResult Index(int entryId)
        {
            Entry entryFromDb = _context.Entries.Include(c => c.Category).Single(e => e.Id == entryId);

            EntryAndCommentViewModel viewModel = new EntryAndCommentViewModel()
            {
                entry = entryFromDb,
                EntryId = entryId
            };
            return View("CommentForm",viewModel);
        }

        [HttpPost]
        public ActionResult Save(Comment comment)
        {

            Entry entryFromDb = _context.Entries.Include(c => c.Category).Single(e => e.Id == comment.EntryId);
            if (!ModelState.IsValid)
            {

                EntryAndCommentViewModel _viewModel = new EntryAndCommentViewModel()
                {
                    entry = entryFromDb,
                    EntryId = comment.EntryId
                };
                return View("CommentForm", _viewModel);
            }

            return View();
        }
    }
}

ViewModel

using Blog.Models;
using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Web;

namespace Blog.ViewModels
{
    public class EntryAndCommentViewModel
    {
        [Required]
        public int EntryId { get; set; }
        public Entry entry { get; set; }

        [Required]
        [StringLength(50)]
        public string Name { get; set; }

        [Required]
        [StringLength(100)]
        [EmailAddress]
        public string EmailAddress { get; set; }

        [Required]
        [StringLength(1000)]
        public string CommentDetails { get; set; }

    }
}

View

@model Blog.ViewModels.EntryAndCommentViewModel
@{
    ViewBag.Title = "CommentForm";
}

<br />

<p class="alert alert-danger">Add <b>Comment</b> to this Post.</p>

<h3>
    <b>
        @Model.entry.Subject
    </b>
</h3>
<p>
    <i>
        Category : <b>@Model.entry.Category.Name</b> - Posted on @Model.entry.PostDate.ToString("dd MMM yyyy")
    </i>
</p>
<p>
    @Model.entry.Body
</p>

<P>
    (0) Comments
</P>

<br />

<h2>Leave a Comment</h2>
<br />
@using (Html.BeginForm("Save", "Comments"))
{
    @Html.HiddenFor(m => m.entry.Id)
    <div class="form-group">
        @Html.LabelFor(m => m.Name)
        @Html.TextBoxFor(m => m.Name, new { @class = "form-control", autofocus = "autofocus", Placeholder = "e.g James Anderson" })
        @Html.ValidationMessageFor(m => m.Name)
    </div>

    <div class="form-group">
        @Html.LabelFor(m => m.EmailAddress)
        @Html.TextBoxFor(m => m.EmailAddress, new { @class = "form-control", Placeholder = "e.g YourEmail@Domain.com" })
        @Html.ValidationMessageFor(m => m.EmailAddress)
    </div>

    <div class="form-group">
        @Html.LabelFor(m => m.CommentDetails)
        @Html.TextAreaFor(m => m.CommentDetails, 4, 8, new { @class = "form-control", Placeholder = "e.g Comment description goes here!" })
        @Html.ValidationMessageFor(m => m.CommentDetails)
    </div>
    <button type="submit" class="btn btn-primary">Save</button>
    <button type="reset" class="btn btn-link">Reset</button>

}

How to fix it ? Thanks

Answer 1

To turn automatic property evaluation on or off

On the Tools menu, click Options. In the Options dialog box, open the Debugging node, and click General. If the Debugging node does not appear, click Show all settings. Select or clear the Enable property evaluation and other implicit function calls check box, and then click OK