MVC 4.0 模型在发布后具有空值答案

【问题标题】：MVC 4.0 model has null values after postMVC 4.0 模型在发布后具有空值
【发布时间】：2016-04-16 15:42:35
【问题描述】：

第一件事：我知道有类似的问题，我已经阅读了很多，但没有一个有帮助。我有一个简单的动作发送模型到视图（从我看到的所有 hiddenfor 字段都是正确的）但是 post 动作没有得到一些属性。这是代码。

控制器：

//
// GET:
public ActionResult EditComputer(int id)
{
    IDataProvider dataProvider = new DataProvider();
    var computer = dataProvider.GetComputer(id);
    return View(computer);
}

//
// POST:
[HttpPost]
public ActionResult EditComputer(COMPUTER computer)
{
    Request.InputStream.Position = 0;
    var result = new System.IO.StreamReader(Request.InputStream).ReadToEnd();
    try
    {
        IDataProvider dataProvider = new DataProvider();
        dataProvider.UpdateComputer(computer);
        return RedirectToAction("EditRoom/" + computer.Room.RoomID);
    }
    catch
    {
        return View(computer);
    }
}

电脑型号：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.NetworkInformation;
using System.Text;
using System.Threading.Tasks;

namespace WebClientDLL
{
    public class COMPUTER
    {
        int _computerID;
        IPAddress _addressIP;
        PhysicalAddress _addressMAC;
        String _namePC;
        ROOM _room;

        public int ComputerID
        {
            get { return _computerID; }
            set { _computerID = value; }
        }

        public IPAddress AddressIP
        {
            get { return _addressIP; }
            set { _addressIP = value; }
        }

        public PhysicalAddress AddressMAC
        {
            get { return _addressMAC; }
            set { _addressMAC = value; }
        }

        public String NamePC
        {
            get { return _namePC; }
            set { _namePC = value; }
        }

        public ROOM Room
        {
            get { return _room; }
            set { _room = value; }
        }
    }
}

房间模型：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WebClientDLL
{
    public class ROOM
    {
        int _roomID;
        String _roomName;
        String _building;

        public int RoomID
        {
            get { return _roomID; }
            set { _roomID = value; }
        }

        public String RoomName
        {
            get { return _roomName; }
            set { _roomName = value; }
        }

        public String Building
        {
            get { return _building; }
            set { _building = value; }
        }
    }
}

查看：

@model WebClientDLL.COMPUTER

@{
    ViewBag.Title = "Edycja komputera";
}

<h2>@ViewBag.Title</h2>

@using (Html.BeginForm()) {
    @Html.AntiForgeryToken()
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Komputer</legend>

        @Html.HiddenFor(model => model.ComputerID)
        @Html.HiddenFor(model => model.Room)
        @Html.HiddenFor(model => model.Room.RoomID)
        @Html.HiddenFor(model => model.Room.RoomName)
        @Html.HiddenFor(model => model.Room.Building)

        <div class="editor-label">
            @Html.LabelFor(model => model.NamePC)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.NamePC)
            @Html.ValidationMessageFor(model => model.NamePC)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.AddressIP)
        </div>
        <div class="editor-field">
            @Html.TextBoxFor(model => model.AddressIP)
            @Html.ValidationMessageFor(model => model.AddressIP)
        </div>

        <div class="editor-label">
            @Html.LabelFor(model => model.AddressMAC)
        </div>
        <div class="editor-field">
            @Html.TextBoxFor(model => model.AddressMAC)
            @Html.ValidationMessageFor(model => model.AddressMAC)
        </div>
        <p>
            <input type="submit" value="Zapisz" />
        </p>
    </fieldset>
}

    <div>
        @Html.ActionLink("Powrót do sali", "EditRoom/" + @Model.Room.RoomID)
    </div>

@section Scripts {
    @Scripts.Render("~/bundles/jqueryval")
}

我从 EditComputer POST 操作的前两行得到：

__RequestVerificationToken=pZR5DUClnJ...
&ComputerID=4
&Room=WebClientDLL.ROOM
&Room.RoomID=1
&Room.RoomName=L2.200
&Room.Building=C-x
&NamePC=PECETx
&AddressIP=192.168.0.24
&AddressMAC=1122334456

虽然所有这些字段都是正确的（如您在上面的 post 字段中所见），但 post 操作中 COMPUTER 参数中的 Room 字段为空。这是为什么呢？

【问题讨论】：

标签： asp.net-mvc null http-post

【解决方案1】：

好的，几天后我设法找出了问题所在。显然它是@Html.HiddenFor(model => model.Room) - mvc 认为它是一个字符串，因为我还没有进行任何验证，所以它没有告诉我任何东西。解决方案是实现接口IModelBinder：

public class COMPUTER : IModelBinder
{
    public object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext)
    {
        var result = bindingContext.ValueProvider.GetValue(bindingContext.ModelName);
        return new COMPUTER();
    }
}

并将其放入 Global.asax：

ModelBinders.Binders.Add(typeof(COMPUTER), new UserModelBinder());

【讨论】：