Question

In ASP.NET MVC 4 Beta, I have an entity with this property:

[DisplayFormat(DataFormatString = "{0:o}", ApplyFormatInEditMode = true)]
public virtual DateTime SavedAt { get; set; }

In a view, generated with the “Controller with read/write actions and views, using EntityFramework” template, I have this code to create an editor for it:

<div class="editor-label">
    @Html.LabelFor(model => model.SavedAt)
</div>
<div class="editor-field">
    @Html.EditorFor(model => model.SavedAt)
    @Html.ValidationMessageFor(model => model.SavedAt)
</div>

Which produces this output:

<div class="editor-label">
    <label for="SavedAt">SavedAt</label>
</div>
<div class="editor-field">
    <input class="text-box single-line" data-val="true" data-val-date="The field SavedAt must be a date." data-val-required="The SavedAt field is required." id="SavedAt" name="SavedAt" type="text" value="2012-03-31T22:45:18.2244059" />
    <span class="field-validation-valid" data-valmsg-for="SavedAt" data-valmsg-replace="true"></span>
</div>

Notice that the date is formatted as “2012-03-31T22:45:18.2244059”.

If I replace the view code fragment with this:

@Html.HiddenFor(model => model.SavedAt)

This code is generated:

<input data-val="true" data-val-date="The field SavedAt must be a date." data-val-required="The SavedAt field is required." id="SavedAt" name="SavedAt" type="hidden" value="31/03/2012 22:45:18" />

Notice that the date is now formatted as “31/03/2012 22:45:18”.

The question is:

Is HiddenFor expected to honor the formatting defined by the DisplayFormat attribute?

If not, what would be a good alternative to have the hidden field output in the desired format?

Answer 1

Is HiddenFor expected to honor the formatting defined by the DisplayFormat attribute?

No, it doesn’t. Only the EditorFor and DisplayFor helpers use the DisplayFormat.

If not, what would be a good alternative to have the hidden field
output in the desired format?

You shouldn’t really care about the format of a hidden field. It’s hidden, nobody sees it. But if for some reason you wanted a custom format you could override the default template with a custom editor template (~/Views/Shared/EditorTemplates/HiddenInput.cshtml):

@if (!ViewData.ModelMetadata.HideSurroundingHtml)
{
    @Html.Encode(ViewData.TemplateInfo.FormattedModelValue)
}
@Html.Hidden("", ViewData.TemplateInfo.FormattedModelValue)

And then decorate your view model property with the [HiddenInput] attribute to indicate that you want this to render as a hidden field:

[DisplayFormat(DataFormatString = "{0:o}", ApplyFormatInEditMode = true)]
[HiddenInput(DisplayValue = false)]
public virtual DateTime SavedAt { get; set; }

And finally:

@Html.EditorFor(x => x.SavedAt)