mvc2中viewModel的问题
最近在看原版的Professinal ASP.net MVC 2。在介绍如何在视图中使用ViewModel绑定dropdownlist，但按书上的说法写好View、Controller和DDinnerFormViewModel后，运行时发现提交修改后无法保存更新。没有任何错误提示，就好像修改没有提交到数据库一样。不知道有没有朋友遇到过这种情况？

DinnerFormViewModel.cs代码：

namespace NerdDinner.Controllers
{
public class DinnerFormViewModel
{
private static string[] _countries = new[]
{
"USA",
"UK",
"CHN"
};

public Dinner Dinner { get; private set; }
public SelectList Countries { get; private set; }

public DinnerFormViewModel(Dinner dinner)
{
Dinner = dinner;
Countries = new SelectList(_countries, dinner.Country);
}
}
}




Edit.aspx视图：

<%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<NerdDinner.Controllers.DinnerFormViewModel>" %>

<asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">
Edit:<%: Model.Dinner.Title %>
</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">

<h2>Edit</h2>

<% using (Html.BeginForm()) {%>
<%: Html.ValidationSummary("Please correct the errors and try again.") %>
<fieldset>
<legend>Fields</legend>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.Title) %>
</div>
<div class="editor-field">
<%: Html.TextBoxFor(model => model.Dinner.Title, new { size = 30, @class = "myclass", style = "font-color:red;" })%>
<%: Html.ValidationMessageFor(model => model.Dinner.Title, "*")%>
</div>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.EventDate)%>
</div>
<div class="editor-field">
<%: Html.TextBoxFor(model => model.Dinner.EventDate)%>
<%: Html.ValidationMessageFor(model => model.Dinner.EventDate, "*")%>
</div>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.Description)%>
</div>
<div class="editor-field">
<%: Html.TextAreaFor(model => model.Dinner.Description)%>
<%: Html.ValidationMessageFor(model => model.Dinner.Description, "*")%>
</div>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.Address)%>
</div>
<div class="editor-field">
<%: Html.TextBoxFor(model => model.Dinner.Address, "*")%>
<%: Html.ValidationMessageFor(model => model.Dinner.Address)%>
</div>

<div class="editor-label">

<%: Html.LabelFor(model => model.Dinner.Country)%>
</div>
<div class="editor-field">
<%: Html.DropDownListFor(model => model.Dinner.Country, Model.Countries) %>
<%: Html.ValidationMessageFor(model => model.Dinner.Country,"*") %>
</div>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.ContactPhone)%>
</div>
<div class="editor-field">
<%: Html.TextBoxFor(model => model.Dinner.ContactPhone, "*")%>
<%: Html.ValidationMessageFor(model => model.Dinner.ContactPhone)%>
</div>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.Latitude)%>
</div>
<div class="editor-field">
<%: Html.TextBoxFor(model => model.Dinner.Latitude, "*")%>
<%: Html.ValidationMessageFor(model => model.Dinner.Latitude)%>
</div>

<div class="editor-label">
<%: Html.LabelFor(model => model.Dinner.Longitude)%>
</div>
<div class="editor-field">
<%: Html.TextBoxFor(model => model.Dinner.Longitude, "*")%>
<%: Html.ValidationMessageFor(model => model.Dinner.Longitude)%>
</div>

<p>
<input type="submit" value="Save" />
</p>
</fieldset>

<% } %>

<div>
<%: Html.ActionLink("Back to List", "Index") %>
</div>

</asp:Content>


DinnersController.cs：

namespace NerdDinner.Controllers
{
public class DinnersController : Controller
{
DinnerRepository Dinners = new DinnerRepository();

public ActionResult Index()
{
var dinners = Dinners.FindUpcomingDinners().ToList();
return View(dinners);
}

public ActionResult Details(int id)
{
Dinner dinner = Dinners.GetDinner(id);
if (dinner == null)
return View("NotFound");
else
return View(dinner);
}

public ActionResult Edit(int id)
{
Dinner dinner = Dinners.GetDinner(id);

return View(new DinnerFormViewModel(dinner));
}

[HttpPost]
public ActionResult Edit(int id, FormCollection formValues)
{
Dinner dinner = Dinners.GetDinner(id);
if (TryUpdateModel(dinner))
{
Dinners.Save();
return RedirectToAction("details", new { id = dinner.DinnerID });
}

return View(new DinnerFormViewModel(dinner));
}

public ActionResult Create()

{
Dinner dinner = new Dinner() {
EventDate = DateTime.Now.AddDays(7)
};
return View(new DinnerFormViewModel(dinner));
}

[HttpPost]
public ActionResult Create(Dinner dinner)
{
if (ModelState.IsValid)
{
dinner.HostedBy = "someuser";
Dinners.Add(dinner);
Dinners.Save();
return RedirectToAction("Details", new { id = dinner.DinnerID });
}
return View(new DinnerFormViewModel(dinner));
}

public ActionResult Delete(int id)
{
Dinner dinner = Dinners.GetDinner(id);
if (dinner == null)
return View("NotFound");
else
return View(dinner);
}

[HttpPost]
public ActionResult Delete(int id, string confirmButton)
{
Dinner dinner = Dinners.GetDinner(id);
if (dinner == null)
return View("NotFound");
Dinners.Delete(dinner);
Dinners.Save();
return View("Deleted");
}
}
}

[解决办法]
DEMO
[解决办法]
我是这样邦—ropDownList的，不知对你有用没有？

Controller层;

public ActionResult FormOtherDemo()
{
List<AreaInfo> areaList = new List<AreaInfo>()
{
new AreaInfo(){Id=1, Name="重庆市"},
new AreaInfo(){Id=2, Name="河北省"},
new AreaInfo(){Id=3, Name="北京市"},
new AreaInfo(){Id=4, Name="天津市"},
new AreaInfo(){Id=5, Name="上海市"},
};
List<SelectListItem> list = (from area in areaList
select new SelectListItem() { Value = area.Id.ToString(), Text = area.Name }).ToList();
ViewBag.AreaList = list;
return View();
}

view层

请选择省份：
<%: Html.DropDownList("AreaInfoId", ViewBag.AreaList as IEnumerable<SelectListItem>, "请选择") %>

[解决办法]
TryUpdateModel(dinner)

->

TryUpdateModel(dinner, "Dinner")