MVC 4 @HTML.HiddenFor are not updating on a postback

Question

Having issues with the view state on a series of page views -- On the initial view of a page in Razor I am using Html.HiddenFor as follows:

    @Html.HiddenFor(x => Model.err)
    @Html.HiddenFor(x => Model.errField)
    @Html.HiddenFor(x => Model.errMessage)
    @Html.HiddenFor(x => Model.IsMove)

which seems to work fine. My hidden input tags contain the correct values. However when I submit the form [HTTPPost] and update the model in my controller action with..

       model.err = transHelper.err;
       model.errField = transHelper.errField;
       model.errMessage = transHelper.errMessage;
       return View(model);

The hidden fields do not seem to update, they contain the original values from the initial view. However When I use these fields in another context within the same razor view like this...

     @*      
        this seems to not update correctly...

    @Html.HiddenFor(x => Model.err)
    @Html.HiddenFor(x => Model.errField)
    @Html.HiddenFor(x => Model.errMessage)
    @Html.HiddenFor(x => Model.IsMove)

        *@
        <input type="hidden" id="err" value="@Model.err" />
        <input type="hidden" id="errField" value="@Model.errField" />
        <input type="hidden" id="errMessage" value="@Model.errMessage" />
        <input type="hidden" id="IsMove" value="@Model.IsMove" />

    </div>

Then the input fields update correctly. I even created a View Helper to help debug, and in all cases, the Model seems to have correct data in HtmlHelper<TModel> -- I even returned the Model as return Json(model); and the data was fine.

At this point I am running with the work around, but does anybody know why @Html.HiddenFor is dirty.

Update: here is my controller actions

  [HttpPost]
   public ActionResult Index(HomePageModel model)
   {


       // process transaction
       Transactionr transr = new Transactionr();
       transr.Process(model);

       model.err = transr.err;
       model.errField = transr.errField;
       model.errMessage = transr.errMessage;

       return View(model);
   }

Here is my view:

        @model App.Models.HomePageModel
    @{
        ViewBag.Title = "Product Categorizer";
    }
    <form id="formData" method="post" action="/Home/Index">
        @Html.AntiForgeryToken()
        <fieldset>
            <div>

            @Html.HiddenFor(model => model.err)
            @Html.HiddenFor(model => model.errField)
            @Html.HiddenFor(model => model.errMessage)
            @Html.HiddenFor(model => model.IsMove)

            <input type="hidden" id="myerr" value="@Model.err" />
            <input type="hidden" id="myerrField" value="@Model.errField" />

            </div>

           <div class="section group">
                <div class="col span_2_of_2">
                     <div class="message" id ="message">
                         @if (Model.err < 0)
                         {
                             <span style="color: purple;">@Model.errMessage (@Model.err) - (@Model.errField)</span>
                         }
                         else if (Model.err > 0)
                         {
                             <span style="color:red;">@Model.errMessage (@Model.err) (@Model.errField)</span>
                         } else {
                            <span>@Model.errMessage (@Model.err) (@Model.errField)</span>
                         }
                         </div>
                     </div>
            </div>

            <div class="section group" id="workspace">
                  @Html.Partial("_WorkspacePartial", Model)
            </div>
              <div class="section group" id="details">
                  @Html.Partial("_DetailPartial", Model)
              </div>


        </fieldset>
        </form>

Here is my model:

 public class HomePageModel
 {
    public int FromStore { get; set; }

    //  the "To" part of the copy/move transaction
    public int ToStore { get; set; }

    // a list of the copy/move transaction
    public List<int> Details { get; set; }


    // true is move false is copy
    public bool IsMove { get; set; }

    // current message
    public int err { get; set; }
    public int errField { get; set; }
    public string errMessage { get; set; }

score 39 · Answer 1 · answered Apr 21 '14 at 15:40

39

The default HtmlHelpers behavior (@Html.HiddenFor, etc) is to behave exactly as you have described.

i.e. any changes you make to the ViewModel on a post are actioned, any changes you return from the Post are received by the view, but on re-rendering WITH HTMLHELPERS, the previous Post-values take precedence over the changed ViewModel values.

Want to "fix" this behavior in a quick + dirty way, clear the ModelState.Clear() prior to returning from the HttpPost ActionMethod !

answered Apr 21 '14 at 15:40

joedotnot

4,810
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91

4

This is very dirty because all the Validation messages are cleared then as well, so be aware! – 321X Jun 15 '16 at 14:40
11

I thought I was going crazy. – agrath Sep 24 '16 at 22:26
I don't get it. There's no Required attribute on any properties of the model. Why returning the view was getting the HiddenFor empty for ONE property ? After doing the ModelState.Clear I was getting the value all right !!! – Marc Roussel Dec 24 '17 at 23:28
***WHY*** _ clear the ModelState.Clear() prior to returning from the HttpPost ActionMethod_ ? – Kiquenet Nov 22 '18 at 21:49
1

Odd behavior (still persists in Razor Pages). It seems to occur because `By default, the validation system treats non-nullable parameters or properties as if they had a [Required] attribute.` according to the docs (https://learn.microsoft.com/en-us/aspnet/core/mvc/models/validation?view=aspnetcore-3.0#required-attribute), but even a single `string` type (nullable) model property used as hidden-input (via `asp-for`) is affected by this behavior, and its value is silently reverted to the previous value. – Nick Nov 11 '19 at 07:34

score 14 · Answer 2 · edited May 19 '20 at 14:40

14

As mentioned by joedotnot this is intended behaviour. Another 'quick fix' for this is to code the html for the hidden field and update only the value from the model eg:

<input type="hidden" id="ErrMessage" name="ErrMessage" value="@Model.ErrMessage">

Use the same id and name as your model property and the updated value will be rendered after postback.

edited May 19 '20 at 14:40

KyleMit

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answered Sep 25 '14 at 09:21

maxscan

191
1
3

This worked like a charm, thanks! – Rob10e Jun 20 '19 at 15:34

Ruslan Georgievskiy · Answer 3 · 2014-10-09T14:25:27.893

I've faced similar problem recently and ended up with writing new simple helper method + 2 overloads. I'm sharing it here in case anybody is still looking for some workaround cause this "feature" is sometimes annoying.

public static class CustomExtensions
{
    public static MvcHtmlString HiddenFor2<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
    {
        ReplacePropertyState(htmlHelper, expression);
        return htmlHelper.HiddenFor(expression);
    }

    public static MvcHtmlString HiddenFor2<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, object htmlAttributes)
    {
        ReplacePropertyState(htmlHelper, expression);
        return htmlHelper.HiddenFor(expression, htmlAttributes);
    }

    public static MvcHtmlString HiddenFor2<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, IDictionary<string, object> htmlAttributes)
    {
        ReplacePropertyState(htmlHelper, expression);
        return htmlHelper.HiddenFor(expression, htmlAttributes);
    }

    private static void ReplacePropertyState<TModel, TProperty>(HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression)
    {
        string text = ExpressionHelper.GetExpressionText(expression);
        string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(text);
        ModelStateDictionary modelState = htmlHelper.ViewContext.ViewData.ModelState;

        if (modelState.ContainsKey(fullName))
        {
            ModelMetadata metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
            ValueProviderResult currentValue = modelState[fullName].Value;
            modelState[fullName].Value = new ValueProviderResult(metadata.Model, Convert.ToString(metadata.Model), currentValue.Culture);
        }
    }
}

Then you just use it as usual from within you view:

@Html.HiddenFor2(m => m.Id)

It worth to mention it works with collections too.

hutchonoid · Answer 4 · 2013-12-18T19:45:29.637

3

I think you should be using them like this instead:

@Html.HiddenFor(x => x.Err)
@Html.HiddenFor(x => x.ErrField)
@Html.HiddenFor(x => x.ErrMessage)
@Html.HiddenFor(x => x.IsMove)

Without seeing your model, I am assuming it looks something like this:

public class ErroViewModel
{
  public string Err { get; set; }
  public string ErrField { get; set; }
  public string ErrMessage { get; set; }
  public bool IsMove { get; set; }
}

If not it should be similar with public properties as above.

Update

In your get do you have the following?

public ActionResult Index(HomePageModel model)
{
   var model = new HomePageModel();
   return View(model);
}

I would also change your form from this:

 <form id="formData" method="post" action="/Home/Index">

To this:

@using (Html.BeginForm("Index", "Home", FormMethod.Post))
{
  // rest of form
}

edited Dec 18 '13 at 19:45

answered Dec 18 '13 at 12:49

hutchonoid

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My Model is using public properties. In terms of the expression, I've tried everything including what you suggest, and it doesn't seem to have any impact. – user799301 Dec 18 '13 at 13:25
Yes, in my get am creating an instance of HomePageModel.. as for the form.. I am doing some form manipulation with jquery so I've coded it like that. – user799301 Dec 19 '13 at 22:12
Hmmm, not sure what the problem could be as it all looks good for me. Still an issue? – hutchonoid Dec 19 '13 at 22:30
Its the `ModelState` that is causing it. See the other answer. – Mat J Apr 21 '14 at 15:47
Why not use `[HttpPost]` ***attribute*** ? – Kiquenet Nov 22 '18 at 21:51
@Kiquenet I would yes, it was just missing from the answer. – hutchonoid Nov 23 '18 at 08:38

score 0 · Answer 5 · answered Nov 27 '15 at 11:49

0

I had a similar issue and solved it like this.

@Html.TextBoxFor(m => m.Email, new { onclick = "this.select()", Value = Model.Email, Placeholder = "E-Mail" })

answered Nov 27 '15 at 11:49

Rune Antonsen

159
1
9

score -1 · Answer 6 · edited Apr 12 '16 at 12:43

-1

You need a key in your view model. If you don't have any property named as Id in your view model, set one of them (expected to be uniqe identifiyer) as key with [Key].

[Key]
Myproperty {get;set;}

edited Apr 12 '16 at 12:43

drneel

2,887
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answered Nov 14 '15 at 14:57

Ilker Ozan Koc

1

score -1 · Answer 7 · answered Mar 06 '16 at 12:08

-1

You can try

<input type="hidden" id="SomeFieldID" name="SomeFieldID" value="@Model.SomeFieldID" />

answered Mar 06 '16 at 12:08

Sumit Kapadia

387
2
9

1

This looks like it was already covered it [maxscan's answer](https://stackoverflow.com/a/26034919/1366033) posted two years earlier – KyleMit May 19 '20 at 14:42

MVC 4 @HTML.HiddenFor are not updating on a postback

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