HttpPost is not fired in ASP.net MVC

Question

In my application there are two text boxes and one button, I want to get the text to the controller when user clicks the button.

I have tried HttpPost but it does not work, here is my code:

View

@model examplemvc1.Models.sample
@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

@Html.TextBoxFor(a=>a.username)
@Html.TextBoxFor(a=>a.password)
<input type="submit" value"button1" />

Controller

namespace examplemvc1.Controllers
{
    public class sampleController : Controller
    {
        //
        // GET: /sample/
        [HttpGet]
        public ActionResult Index()
        {
            return View();
        }
        [HttpPost]
        public ActionResult Index(sample sam)
        {
            return View(sam);
        }
    }
}

model

namespace examplemvc1.Models
{
    public class sample
    {
        public string username { get; set; }
        public string password { get; set; }
    }
}

Answer 1

At the request of the OP:

@model examplemvc1.Models.sample
@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>
@using (Html.BeginForm())
{
    @Html.TextBoxFor(a=>a.username)
    @Html.TextBoxFor(a=>a.password)

    <input type="submit" value"button1" />
}

Answer 2

You have to add a form which will be posted to your controller

@using (Html.BeginForm())
{
    @Html.TextBox("Name");
    @Html.Password("Password");
    <input type="submit" value="Sign In">
}

Produces the following form element

<form action="/Original Controller/Original Action" action="post">