asp.net-mvc - 在 POST Edit 中保存表单的正确方法？

Question

一般来说，我对 asp .net 和 mvc 很陌生。我正在实现 Controller 的 GET 编辑和 POST 编辑方法。我正在使用强类型 View 来编辑表单。我将模型传递回 POST 编辑方法，但我不知道如何保存它。这是我到目前为止所拥有的......我知道的并不多。

    [HttpPost]
    public ActionResult ModifyContract(ModContract mod)
    {
        // submit modified contract
        if (ModelState.IsValid)
        {
            OutlookMediaEntities1 db = new OutlookMediaEntities1();
            db.ObjectStateManager.ChangeObjectState(mod, EntityState.Modified);

            // save changes
            db.SaveChanges();

            return RedirectToAction("ContractDetails", "Contract", new { id = (int) ViewData["contractid"] });
        }
        else
        {
            ModelState.AddModelError("", "Missing necessary information");
            return View();
        }
    }

我在 db.ObjectStateManager... 行上收到 InvalidOperationException。我看到一些说这可能是因为我没有分配主键并注意到我的 ModAds 类(如下)不包含主键。添加了它，但我得到了同样的错误。这是堆栈跟踪:

[InvalidOperationException: The ObjectStateManager does not contain an ObjectStateEntry with a reference to an object of type 'oulookmediaweb.Models.ModContract'.]
   System.Data.Objects.ObjectStateManager.ChangeObjectState(Object entity, EntityState entityState) +278
   oulookmediaweb.Controllers.ContractController.ModifyContract(ModContract mod) in C:\Users\georgiev.1\Outlook4\oulookmediaweb\Controllers\ContractController.cs:1113
   lambda_method(Closure , ControllerBase , Object[] ) +163
   System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters) +17
   System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters) +205
   System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters) +27
   System.Web.Mvc.Async.c__DisplayClass42.b__41() +28
   System.Web.Mvc.Async.c__DisplayClass8`1.b__7(IAsyncResult _) +12
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +57
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult) +50
   System.Web.Mvc.Async.c__DisplayClass39.b__33() +58
   System.Web.Mvc.Async.c__DisplayClass4f.b__49() +237
   System.Web.Mvc.Async.c__DisplayClass37.b__36(IAsyncResult asyncResult) +12
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +57
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult) +50
   System.Web.Mvc.Async.c__DisplayClass2a.b__20() +24
   System.Web.Mvc.Async.c__DisplayClass25.b__22(IAsyncResult asyncResult) +126
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +57
   System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +45
   System.Web.Mvc.c__DisplayClass1d.b__18(IAsyncResult asyncResult) +14
   System.Web.Mvc.Async.c__DisplayClass4.b__3(IAsyncResult ar) +25
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
   System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +61
   System.Web.Mvc.Async.c__DisplayClass4.b__3(IAsyncResult ar) +25
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
   System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +49
   System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10
   System.Web.Mvc.c__DisplayClass8.b__3(IAsyncResult asyncResult) +28
   System.Web.Mvc.Async.c__DisplayClass4.b__3(IAsyncResult ar) +25
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +49
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8970141
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184

这也是模型:

public class ModContract
{
    public int contract_id;
    public string contract_name { get; set; }
    public List<ModAds> ads;

    public string print_product_id { get; set; }
    public string print_ad_option_id { get; set; }
}

public class ModAds
{
    public int contr_ad_id;
    public string name;
    public string product_name;
    public string adv_product;
    public List<string> editions;
    public double freq_disc;
    public double other_dis_dol;
    public double? other_dis_per;
    public string non_cash_note;
    public double non_cash_cons;
}

我不知道如何保存通过的模型。我看过的所有教程都有非常简单的模型，并且保存是通过类似的方式完成的，

db.Entry(model).State = EntityState.Modified;
db.SaveChanges();

当我把第一行放在我的代码中时，它甚至没有编译；它说没有方法入口。模型如何从表单字段中获取新值？ View 如何知道将该模型作为参数传递？是因为 View 是强类型的吗？如果不是，会发生什么？ View 是否会汇总所有输入并选择表单元素中的内容并将它们放入模型中？我只是对这一切如何运作感到困惑。最重要的是，如何保存模型？

任何帮助或帮助链接表示赞赏!提前致谢!

Answer 1

The first line doesn't even compile when I put it in my code; it says there's no method Entry.

这很可能是因为您使用的是旧版本的 EF。在 4.1 之前，EF 使用 ObjectContext没有 Entry方法。 EF 4.1+ 使用具有 Entry 的 DbContext方法。此外，您还有一个名为 mod 的参数。并且您正在保存一个名为 model 的变量，这是拼写错误吗？有 a great tutorial on EF and MVC here .

How does the model get the new values from the form fields? How does the view know to pass that model as a parameter?

它被称为 model binding that is greatly explains here .

Is it because the view is strongly-typed?

是的

What happens if it's not?

只要正确命名 HTML 元素，您仍然可以利用模型绑定(bind)。例如，您有一个 Controller 方法声明为:

[HttpPost]
ActionResult Product(int id, string name) {
}

如果您命名与参数名称匹配的元素，模型绑定(bind)器可以完成它的工作:

<input type="hidden" name="id"/>
<input type="text" name="name" id="name"/>

Does the view round up all the input and select stuff in a form element and put them in the model?

请参阅模型绑定(bind)。

And most importantly, how do I save the model?

[HttpPost]
public ActionResult ModifyContract(ModContract mod)
{
    // do some validation or anything else you need to do here
    // then save your entity
    db.Entry(mod).State = EntityState.Modified;
    db.SaveChanges();
}