ASP.Net MVC 2.0 Html.HiddenFor HtmlHelper extension doesn't return the Value

Question

We're trying to be type-safe in our views and use the new ExpressionInputExtenssion HtmlHelpers, but we are seeing some inconsistent results. We have a view that looks like this:

ViewData.Model.FooID = <%= ViewData.Model.FooID %><
Model.FooID = <%= Model.FooID  %>       
<%= Html.HiddenFor(x=>x.FooID) %>

But what we see in the rendered view is this:

ViewData.Model.FooID = 515b0403-e75b-4bd7-9b60-ef432f39d338
Model.FooID = 515b0403-e75b-4bd7-9b60-ef432f39d338    
<input id="FooID" name="FooID" type="hidden" value="" />

I can manually add this:

<input id="FooID" name="FooID" type="hidden" value="<%= Model.FooID %>" />

But now we are no longer, but surprisingly when I do, The Html.HiddenFor always has the correct value.

Edgarin · Accepted Answer · 2010-08-16 05:50:24Z

3

Take a look at this: http://blogs.msdn.com/b/simonince/archive/2010/05/05/asp-net-mvc-s-html-helpers-render-the-wrong-value.aspx

answered Aug 16, 2010 at 5:50

Edgarin

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Andre Gallo · Accepted Answer · 2009-11-16 02:52:33Z

2

It looks like the model binder that is behind the extension method cannot convert you FoodID datatype to a string. Is your data type a regular GUID?

I known there are overloads for this extension method for working with binary but I'm not sure about GUIDs ....

Have u tried debbuging it?

answered Nov 16, 2009 at 2:52

Andre Gallo

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3 Comments

Mark Over a year ago

It is actually a Nullable<Guid>? No I haven't debugged the HtmlHelper extension just yet. The model binder would wire up the model before the controller action though correct? I can step through my controller action, see me model with the correct value, and even in the view I can see the model with the correct value. I can even see the model value evaluate in the view if I access the property directly.

Andre Gallo Over a year ago

I just tried this and works fine: <%= Html.Hidden("CustomerGuid", item.CustomerGuid) %> At least this way you can still be type-safe ...

Mark Over a year ago

Yea. I could do that, but I was trying to avoid the "CustomerGuid" control name. It would be nice if they would just give you an extension method like Html.IdFor(x=>x.CustomerGuid) and then I could throw it wherever I need. I don't mind writing the HTML, just naming the control. Thanks!

user348802 · Accepted Answer · 2010-05-25 09:12:27Z

1

I encountered similiar problem, I have one element of the model is hiddeninput, I can see the correct value of this element while displaying view(as debug I show it to check there's correct value in the view), but once I post the view, the return value of this element keeps the first time it's been set, whatever I refresh the display and be sure the correct value shown on the view, but the return value just keep the value been set at first time. This is odd.

answered May 25, 2010 at 9:12

user348802

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Comments

Sasha · Accepted Answer · 2013-02-19 09:52:36Z

You can also roll your own extension that use the value from the property

@Html.HiddenForField(m => m.Location.CityRequired)

public static class HiddenExtensions
{
    public static MvcHtmlString HiddenForField<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression) where TModel : class
    {
        var metadata = ModelMetadata.FromLambdaExpression(expression, htmlHelper.ViewData);
        var value = metadata.Model;
        return htmlHelper.HiddenForField(expression, value);
    }

    public static MvcHtmlString HiddenForField<TModel, TValue>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TValue>> expression, object value) where TModel : class
    {
        string htmlFieldName = ExpressionHelper.GetExpressionText(expression);
        string fullName = htmlHelper.ViewContext.ViewData.TemplateInfo.GetFullHtmlFieldName(htmlFieldName);
        var tag = new TagBuilder("input");
        tag.GenerateId(fullName);
        tag.Attributes.Add("type", "hidden");
        tag.Attributes.Add("name", fullName);
        tag.Attributes.Add("value", value != null ? value.ToString() : string.Empty);
        return new MvcHtmlString(tag.ToString());
    }
}

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