实体框架TryUpdateModel子对象？

Question

我知道你们大多数人会建议我应该使用特定于我使用的窗体的ViewModels，但我很好奇为什么我的子对象不能绑定到TryUpdateModel上。

@using (Html.BeginForm()) { 
    @Html.ValidationSummary(true) 
    <fieldset> 
     <legend>User</legend> 

     @Html.HiddenFor(model => model.UserId) 
    @Html.HiddenFor(model => model.PrimaryAddress.AddressId) 
    <div class="editor-label"> 
      @Html.LabelFor(model => model.PrimaryAddress.FirstName) 
     </div> 
     <div class="editor-field"> 
      @Html.EditorFor(model => model.PrimaryAddress.FirstName) 
      @Html.ValidationMessageFor(model => model.PrimaryAddress.FirstName) 
     </div> 

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

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

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

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

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

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

而控制器代码：

[HttpPost] 
public ActionResult Edit(int id, FormCollection form) 
{ 
    var user = Token.DB.Users.Include("PrimaryAddress").Single(x => x.UserId == id); 
    if (TryUpdateModel(user, new string[] { "UserName", "Email", "IsApproved", "IsEmployee", "PrimaryAddress.FirstName", "PrimaryAddress.LastName" })) 
    { 
     try 
     { 
      Token.DB.SaveChanges(); 
      return RedirectToAction("index"); 
     } 
     catch (Exception ex) 
     { 
      while (ex.InnerException != null) 
       ex = ex.InnerException; 
      if (ex.Message.ToLowerInvariant().Contains("unique")) 
       ModelState.AddModelError("UserName", "UserName already exists"); 
     } 
    } 
    return View(User); 
} 

代码不抛出任何异常，它只是不填充表单中的user.PrimaryAddress.FirstName或user.PrimaryAddress.LastName。我想知道为什么？

我已经知道我可以用特定的ViewModel解决问题并在后台映射信息。我也可以这样做：

<!-- Edit.cshtml --> 
<div class="editor-field"> 
    @Html.EditorFor(model => model.PrimaryAddress.FirstName, null, "FirstName") 
    @Html.ValidationMessageFor(model => model.PrimaryAddress.FirstName) 
</div> 

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

// UsersController.cs 
if (TryUpdateModel(user, new string[] { "UserName", "Email", "IsApproved", "IsEmployee"}) 
&& TryUpdateModel(user.PrimaryAddress, new string[] {"FirstName", "LastName" })) 

所以真正的问题是为什么它没有在第一个例子中绑定？

Answer 1

所以真正的问题是为什么它没有在第一个例子中绑定？

您的问题的答案非常简单：UpdateModel，TryUpdateModel或[Bind]属性都不支持包含/排除属性列表中的“嵌套属性”。因此，请妥善做好事情并使用视图模型。防范大规模财产分配攻击只是为什么您应该使用视图模型的数百万个原因之一。那么，您似乎已经通过执行第二个TryUpdateModel找到了解决方法，但是如果您在此域对象上有很多属性，那么您的控制器操作代码可能会很快变成意大利面条管道代码。

Answer 2

我发现一些情况下，我想做同样的事情。我还发现子对象不起作用，但子对象的列表/集合确实很奇怪。

我找到了一个很好的link描述如何解决这个问题。

它结束了看起来像这样：

[AcceptVerbs(HttpVerbs.Post)] 
public ActionResult Save(int id, FormCollection collection) 
{ 
    User user = null; 
    if (id == 0) 
    { 
     user = new User(); 
     UpdateModel(user, "User"); 
     user.Contact = new Contact(); 
     UpdateModel(user.Contact, "User.Contact"); 
     user.Contact.Addresses = new EntitySet<Address>(); 
     UpdateModel(user.Contact.Addresses, "User.Contact.Addresses"); 
    } 
    else 
    { 
     // get current user object from DB, however you normally do this is fine. 
     user = userRepository.GetById(id); 
     UpdateModel(user, "User"); 
     UpdateModel(user.Contact, "User.Contact"); 
     UpdateModel(user.Contact.Addresses, "User.Contact.Addresses"); 
    } 
    // at this point, model "user" and children would have been updated. 
} 
...