how I can bind my datasource to view?

问题:

I have serious problem I can not pass my data to controller when the form submitted how I can solve this ?

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

and my view :

@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

回答1:

Every type that you are trying to use as action parameter must have a default parameterless constructor. Otherwise the default model binder will not be able to instantiate it and populate its properties.

That's why you should never use your domain models in views. You should define and use view models which are classes specifically design to meet the requirements of a given view. Then the controller action will map back and forth between the view models and the domain models. Like this:

[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 
    ...
}

That's as far as best practices are concerned. If your application has already been polluted and refactoring towards view models is not possible at the moment you have two possibilities:

1. Write a custom model binder for the BindableEntity type so that you manually invoke the proper constructor in the CreateModel method.
2. Add a default parameterless constructor to the BindableEntity type.

3. Use the TryUpdateModel method:

   [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 
       ...
   }
   

回答2:

I assume you have only defined constructors with parameters? To fix this, you need to add this line of code

public BindableEntity()
{ }

To your EnterpriseFramework.Entity.Synchronization.BindableEntity class.

This will define a parameter-less constructor and will allow you to use it as you desire, although you do need to define a ViewModel in order to use MVC in the way it was designed.