回发时MVC模型为空

Question

我有这个模型，客户。当我获得带有id的信息时，它的工作正常。

喜欢;

/客户/实体/ 5

    @model ProgSpace.Models.Customer

    @{
        ViewBag.Title = Model.Name;
        Layout = "~/Views/Shared/_MainLayout.cshtml";
    }

    @section bodypane
    {
        @using (Html.BeginForm("Entity", "Customer", FormMethod.Post, new { @enctype = "multipart/form-data" }))
        {

            @Html.AntiForgeryToken()



            <div class="col-md-12">


                <div class="col-md-1">
                    <label>Customer No:</label>
                    <h4># @(Model.ID) </h4>
                </div>



                <div class="clearfix"></div><br />

                <div class="col-md-2">

                    <div class="col-md-12">
                        <div class="col-md-12 fileupload fileupload-exists" data-provides="fileupload">

                            <div class="fileupload-preview fileupload-exists thumbnail" style="width: 200px; height: 150px;">
                                <img src="@Model.Picture.Path" />

                            </div>
                            <div>
                                <span class="btn btn-default btn-file">
                                    <span class="fileupload-new">Add Pic </span>
                                    <span class="fileupload-exists">Change</span><input name="file"  id="file" type="file">
                                </span>
                                <a href="#" class="btn fileupload-exists" data-dismiss="fileupload">Remove</a>
                            </div>
                        </div>
                    </div>
                </div>


                <div class="col-md-10">
                    <div class="col-md-3">
                        <label>Name *</label>
                        @Html.TextBoxFor(model => model.Name, new { @class = "form-control"})
                    </div>




                    <div class="col-md-3">
                        <label>Company</label>
                        @Html.TextBoxFor(model => model.Contact.Company, new { @class = "form-control"})
                    </div>

                    <div class="col-md-3">
                        <label>Phone </label>
                        @Html.TextBoxFor(model => model.Contact.Phone, new { @class = "form-control" })
                    </div>


                </div>


                <div class="clearfix"><br /></div>
                <p>&nbsp;</p>

                <div class="col-md-12">
                    <div class="btn-group">

                        <button class="btn btn-danger btn-lg">Cancel</button>

                        <button type="submit" class="btn btn-success btn-lg">Send</button>

                    </div>
                </div>

            </div>

        }
    }

在控制器中我有这些动作。

   public ActionResult Entity(int id)
    {
        Customer cust= sis.Customers.Where(t => t.ID == id).FirstOrDefault();
        return View(cust);
    }

    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Entity(Customer cust, HttpPostedFileBase file)
    {

        if (ModelState.IsValid)
        {
            /* Do something */
        }
        else
        {

        }


        return View(cust);
    }

当动词是GET时，没关系。但是当我发布这个表单并且当第二个动作（HttpPost动作）启动时，视图会抛出错误..

未将对象引用设置为对象的实例

标记 Model.ID 在视图中为空。

          <div class="col-md-1">
                    <label>Customer No:</label>
                    <h4># @(Model.ID) </h4> ---> THIS HERE THROWS NULL EXCEPTION
                </div>

我尝试为Model.ID添加HiddenFor，如

 @Html.HiddenFor(t => t.ID)

但它没有改变任何东西。

如何再次使用相同的上下文返回相同的视图？