Question

我有严重的问题我在表格提交时如何解决这个问题时无法将数据传递给控制器？

//int controller class
[HttpPost]
public ActionResult Index(EnterpriseFramework.Entity.Synchronization.BindableEntity model)
{
    //do something
}

和我的观点：

@model EnterpriseFramework.Entity.Synchronization.BindableEntity 

<p>
    @using (Html.BeginForm())
    {
        <fieldset>
            <legend>title</legend>
            <div>
                @Html.HiddenFor(m => (m.Underlay.Entity as AutomationTest.Models.DTO.Letter).oau_Letter_Id)
            </div>
            <div>                
                @Html.LabelFor(m => (m.Underlay.Entity as AutomationTest.Models.DTO.Letter).oau_Letter_Number)
                @Html.TextBoxFor(m => (m.Underlay.Entity as AutomationTest.Models.DTO.Letter).oau_Letter_Number)
            </div>
            <div>
                @{
                    EnterpriseFramework.Entity.Synchronization.DataSource ds = Model.GetRelation("lnkLetterReceiver");
                    foreach (EnterpriseFramework.Entity.Synchronization.BindableEntity  item in ds)
                    {
                        AutomationTest.Models.DTO.LetterReceiver childRece = item.Underlay.Entity as 
                            AutomationTest.Models.DTO.LetterReceiver;
                        <div>                            
                            @Html.LabelFor(c=> childRece.oau_LetterReceiver_Name)
                            @Html.TextBoxFor(c=> childRece.oau_LetterReceiver_Name)
                        </div>
                    }
                }              
            </div>
            <div>
                <input type="submit" name="Confirm" value="Confirm" />
            </div>
        </fieldset>
    }
</p>

Server Error in '/' Application.
--------------------------------------------------------------------------------

No parameterless constructor defined for this object. 
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace: 


[MissingMethodException: No parameterless constructor defined for this object.]
   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache) +98
   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipVisibilityChecks, Boolean skipCheckThis, Boolean fillCache) +241
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +69
   System.Web.Mvc.DefaultModelBinder.CreateModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Type modelType) +199
   System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +572
   System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +449
   System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +317
   System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +117
   System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +343
   System.Web.Mvc.Controller.ExecuteCore() +116
   System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +97
   System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10
   System.Web.Mvc.<>c__DisplayClassb.<BeginProcessRequest>b__5() +37
   System.Web.Mvc.Async.<>c__DisplayClass1.<MakeVoidDelegate>b__0() +21
   System.Web.Mvc.Async.<>c__DisplayClass8`1.<BeginSynchronous>b__7(IAsyncResult _) +12
   System.Web.Mvc.Async.WrappedAsyncResult`1.End() +62
   System.Web.Mvc.<>c__DisplayClasse.<EndProcessRequest>b__d() +50
   System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f) +7
   System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22
   System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8897857
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +184

Answer 1

您尝试用作操作参数的每个类型都必须具有默认的无参数构造函数。否则，默认模型绑定器将无法实例化它并填充其属性。

这就是为什么你永远不应该在视图中使用你的域模型。您应该定义和使用视图模型，这些视图模型是专门设计的类，以满足给定视图的要求。然后，控制器操作将在视图模型和域模型之间来回映射。像这样：

[HttpPost]
public ActionResult Index(MyViewModel model)
{  
    if (!ModelState.IsValid)
    {
        // There were validation errors => redisplay the view
        return View(model);
    }

    // the model is valid => map the view model to a domain model and process 
    ...
}

就最佳实践而言，这是最重要的。如果您的应用程序已被污染，目前无法对视图模型进行重构，您有两种可能：

为BindableEntity类型编写自定义模型绑定器，以便您在CreateModel方法中手动调用正确的构造函数。
将默认无参数构造函数添加到BindableEntity类型。

使用TryUpdateModel方法：

[HttpPost]
public ActionResult Index()
{  
    var model = new BindableEntity(WHATEVER);
    if (!TryUpdateModel(model) || !ModelState.IsValid)
    {
        // There were validation errors => redisplay the view
        return View(model);
    }

    // the model is valid => process 
    ...
}

Answer 2

我假设您只定义了带参数的构造函数？要解决此问题，您需要添加此行代码

public BindableEntity()
{ }

致EnterpriseFramework.Entity.Synchronization.BindableEntity班。

这将定义一个无参数构造函数，并允许您根据需要使用它，尽管您需要定义ViewModel以便按照设计的方式使用MVC。

我如何绑定我的数据源来查看？

2 个答案: