Strange Behavour with MVC Razor Syntax - asp.net-mvc

Question

I have a contact us form which is reused for varying purposes in the site
The rule is that if certain fields are already pre-populated ie the email address or subject is known then these should not be displayed ie becomes a HiddenFor
For the email this works fine, but subject it doesn't and im completely confused as they are identical string fields both required with a MaxLength of 100
#model List<TJI.ObjectModel.Entities.Form>
...
if (string.IsNullOrEmpty(Model.Email))
{
<div class="form-group">
#Html.LabelFor(model => model.Email, new {#class = "control-label col-sm-3 col-md-2"})
<div class="col-sm-8 col-md-4">
#Html.TextBoxFor(model => model.Email, new {#class = "form-control"})
</div>
<div class="col-sm-1 col-md-1">
#Html.ValidationMessageFor(m => m.Email, "*")
</div>
</div>
}
else
{
<div>
#Html.HiddenFor(model => model.Email)
</div>
}
if (string.IsNullOrEmpty(Model.Subject))
{
<div class="form-group">
#Html.LabelFor(model => model.Subject, new {#class = "control-label col-sm-3 col-md-2"})
<div class="col-sm-8 col-md-9">
#Html.TextBoxFor(model => model.Subject, new {#class = "form-control"})
</div>
<div class="col-sm-1 col-md-1">
#Html.ValidationMessageFor(model => model.Subject, "*")
</div>
</div>
}
else
{
<div>
#Html.HiddenFor(model => model.Subject)
</div>
}
...
public class Form : EntityBase
{
...
[Required]
[MaxLength(100)]
public string Email { get; set; }
[Required]
[MaxLength(100)]
public string Subject { get; set; }
....
}

Answer 1

After all that i realized i didn't pass the subject accross to the ViewModel in the controller
public ActionResult Contact(string contactTypeEnum, string subject, string body, string department )
{
if (string.IsNullOrEmpty(department))
{
department = Department.None.ToString();
}
var user = GetCurrentUser();
var model = new FormViewModel
{
Subject = subject,
Department = (Department) Enum.Parse(typeof (Department), department)
};
if (user != null)
{
model.Name = user.Name;
model.Email = user.Email;
}
CacheEntity(model);
return IsAjax() ? (ActionResult) PartialView("ContactDetail", model) : View(model);
}