Q:

Perform validation on hidden fields

I have the view below:
    @Html. LabelFor(m => m.CompanyPostCode)
    @Html. TextBoxFor(m => m.CompanyPostCode)

    @Html. LabelFor(m => m.CompanyCity)
    @Html. TextBoxFor(m => m.CompanyCity)

    @Html. HiddenFor(m => m.CompanyCityID)

All attributes are marked as [Required] in my view model.  Then problem is that my CompanyCityID (marked as Required) is hidden and thus no validation is done in the view.  If I show this attribute in my view the validation is done.  

My question: is it possible to perform a validation on a hidden field?  A workaround exist? 
It may seems a little strange to validate a hidden field.  The reason is that this field is filled from jQuery based on special rules.  If it is not filled, I know something is not valid on the view. 
Thanks. 

A:

The possible reason can be that there is ignore: ':hidden' line in jquery.validate.unobtrusive.js file. 
After 1.9.0 version it is a default behaviour.  You can fix that manually by adding
$.validator.setDefaults({ ignore: [] });

As you can see here

Another change should make the setup of forms with hidden elements
  easier, these are now ignored by default (option “ignore” has
  “:hidden” now as default).  In theory, this could break an existing
  setup.  In the unlikely case that it actually does, you can fix it by
  setting the ignore-option to “[]” (square brackets without the
  quotes).