Possible bug in ASP.NET MVC with form values being replaced

Question

I appear to be having a problem with ASP.NET MVC in that, if I have more than one form on a page which uses the same name in each one, but as different types (radio/hidden/etc), then, when the first form posts (I choose the 'Date' radio button for instance), if the form is re-rendered (say as part of the results page), I seem to have the issue that the hidden value of the SearchType on the other forms is changed to the last radio button value (in this case, SearchType.Name).

Below is an example form for reduction purposes.

<% Html.BeginForm("Search", "Search", FormMethod.Post); %>
  <%= Html.RadioButton("SearchType", SearchType.Date, true) %>
  <%= Html.RadioButton("SearchType", SearchType.Name) %>
  <input type="submit" name="submitForm" value="Submit" />
<% Html.EndForm(); %>

<% Html.BeginForm("Search", "Search", FormMethod.Post); %>
  <%= Html.Hidden("SearchType", SearchType.Colour) %>
  <input type="submit" name="submitForm" value="Submit" />
<% Html.EndForm(); %>

<% Html.BeginForm("Search", "Search", FormMethod.Post); %>
  <%= Html.Hidden("SearchType", SearchType.Reference) %>
  <input type="submit" name="submitForm" value="Submit" />
<% Html.EndForm(); %>

Resulting page source (this would be part of the results page)

<form action="/Search/Search" method="post">
  <input type="radio" name="SearchType" value="Date" />
  <input type="radio" name="SearchType" value="Name" />
  <input type="submit" name="submitForm" value="Submit" />
</form>

<form action="/Search/Search" method="post">
  <input type="hidden" name="SearchType" value="Name" /> <!-- Should be Colour -->
  <input type="submit" name="submitForm" value="Submit" />
</form>

<form action="/Search/Search" method="post">
  <input type="hidden" name="SearchType" value="Name" /> <!-- Should be Reference -->
  <input type="submit" name="submitForm" value="Submit" />
</form>

Please can anyone else with RC1 confirm this?

Maybe it's because I'm using an enum. I don't know. I should add that I can circumvent this issue by using 'manual' input () tags for the hidden fields, but if I use MVC tags (<%= Html.Hidden(...) %>), .NET MVC replaces them every time.

Many thanks.

Update:

I've seen this bug again today. It seems that this crops its head when you return a posted page and use MVC set hidden form tags with the Html helper. I've contacted Phil Haack about this, because I don't know where else to turn, and I don't believe that this should be expected behaviour as specified by David.

Answer 1

Yes, this behavior is currently by design. Even though you're explicitly setting values, if you post back to the same URL, we look in model state and use the value there. In general, this allows us to display the value you submitted on postback, rather than the original value.

There are two possible solutions:

Solution 1

Use unique names for each of the fields. Note that by default we use the name you specify as the id of the HTML element. It's invalid HTML to have multiple elements have the same id. So using unique names is good practice.

Solution 2

Do not use the Hidden helper. It seems like you really don't need it. Instead, you could do this:

<input type="hidden" name="the-name" 
  value="<%= Html.AttributeEncode(Model.Value) %>" />

Of course, as I think about this more, changing the value based on a postback makes sense for Textboxes, but makes less sense for hidden inputs. We can't change this for v1.0, but I'll consider it for v2. But we need to think through carefully the implications of such a change.