MVC 4模型绑定返回null

Question

I'm having trouble with model binding in MVC. I have a class:

public class UserSurvey
{
    public int Id { get; set; }
    public virtual Survey Survey { get; set; }
}

Which is the model for a view:

@model SurveyR.Model.UserSurvey

<form id="surveyForm">
    <div class="container survey">
        @Html.HiddenFor(x=>x.Id)

        @Html.EditorFor(x => x.Survey.Steps)
    </div>

    <input type="button" value="Submit" id="btnSubmit"/>
</form>

And then for the submit the controller takes a class:

public class SurveyResponseViewModel
{
    public int Id { get; set; }
    public Survey Survey { get; set; }
}

[HttpPost]
public ActionResult Submit(SurveyResponseViewModel surveyResponse)
{
    ...
}

When I debug the submit the surveyResponse.Survey object is populated as it should be but the surveyResponse.Id value is 0 when it should be 1.

I can see the Id=1 being passed back in the submit but the model binding doesn't seem to hook it up.

Any help would be greatly appreciated!

Kev

EDIT: The rendered html looks like this:

<form id="surveyForm">
    <div class="container survey">
        <input data-val="true" data-val-number="The field Id must be a number." data-val-required="The Id field is required." id="Id" name="Id" type="hidden" value="1" />

So yes the value appears there and is also passed in the submit if I look using dev tools.

EDIT 2: The Form data in dev tools definitely contains "Id:1".

Answer 1

Your Code seems to be fine.Try passing the id value explicitly as another parameter like below

[HttpPost]
public ActionResult Submit(SurveyResponseViewModel surveyResponse , int Id )
{

  surveyResponse.Id = Id
}

Answer 2

I have tested. Its working fine.

    public ActionResult test1()
    {
        var model = new UserSurvey();
        model.Id = 10;
        return View(model);
    }
    [HttpPost]
    public ActionResult test1(SurveyResponseViewModel surveyResponse)
    {
        var x = surveyResponse.Id; // returns 10
        return View(new UserSurvey());
    }

    public class SurveyResponseViewModel
    {
        public int Id { get; set; }
        public Survey Survey { get; set; }
    }

    public class UserSurvey
    {
        public int Id { get; set; }
        public virtual Survey Survey { get; set; }
    }

    public class Survey
    {
        public string Steps { get; set; }
    }

@model TestWeb.Controllers.UserSurvey

@using (Html.BeginForm())
{
    <div class="container survey">
        @Html.HiddenFor(x=>x.Id)

        @Html.EditorFor(x => x.Survey.Steps)
    </div>

    <input type="submit" value="Submit" id="btnSubmit"/>
}