submit button doesn't pass input from textbox - asp.net-mvc

Question

Basically i have an input box in which an user can type in his email, and a button that submits the email. I can press the button, and it redirects to my "details" page. However, the input from the texbox is not passed to my controller.
View:
#using (Html.BeginForm("Index", "Home", FormMethod.Post))
{
<div class="form-group form-inline">
<label class="margin20">Sign up for newsletter</label>
#Html.TextBoxFor(Model => Model.Email, new { name= "mail", Class = "form-control", Style = "display:inline-block; max-width:200px", Placeholder="Example#Example.com" })
<input type="submit" class="btn btn-default" style="display:inline-block" id="emailSignup"/>
</div>
}
Controllers
public class HomeController : Controller
{
// GET: Home
public ActionResult Index()
{
return View();
}
[HttpPost]
public ActionResult Index(string mail)
{
return RedirectToAction("details", new {address = mail });
}
public ActionResult details(string address)
{
EmailSignup person = new EmailSignup { Email = address};
return View(person);
}
}
i left the model out, because it basically is 1 property.

Answer 1

Your
#Html.TextBoxFor(Model => Model.Email, ...)
is generating an input with name="Email".
Note that new { name = "mail" } does absolutely nothing fortunately (look at the html your generating) because if it did, it would screw up the model binding process - the whole purpose of using the HtmlHelper methods is to bind to your model.
You could change the method to
[HttpPost]
public ActionResult Index(string email)
and the parameter will be correctly bound, however your method should be
[HttpPost]
public ActionResult Index(XXX model)
{
if (!ModelState.IsValid)
{
return View(model);
}
return RedirectToAction("details", new { address = model.Email });
}
where XXX is the model that you declared in the view (i.e. with #model XXX), so that you get correct model binding and can take into account validation.
Note also that you property should be
[Display(Name = "Sign up for newsletter")]
[Required("Please ...")] // assuming you want to ensure a value is submitted
[EmailAddress] // assuming you want a valid email
public string Email { get; set; }
and then the view will be
#Html.LabelFor(m => m.Email) / correctly generates a label associated with the input
#Html.TextBoxFor(m => m.Email, new { #class = "form-control", placeholder="Example#Example.com" })
#Html.ValidationMessageFOr(m => m.Email)
and I recommend adding another class name and using css rather than you inline style = ".." element