<form action="/home/showdata" method="post">
  <input type="text" name="arr.username" />
  <input type="text" name="arr.password" />
  <input type="text" name="arr.email" />
</form>

public class HomeController : Controller
{
    [HttpPost]
    public ActionResult ShowData(Array data)
    {
        return Content(data.username + data.password + data.email);
    }
}

public ActionResult ShowData(Array data)

public ActionResult ShowData(YourModelNameHere data)

public class YourModelNameHere
{
    public string username {get; set;}
    public string password {get; set;}
    public string email {get; set;}
}

<form action="/home/showdata" method="post">
  <input type="text" name="username" />
  <input type="text" name="password" />
  <input type="text" name="email" />
</form>

public class HomeController : Controller
{

    [HttpPost]
    public ActionResult ShowData(FormCollection data)
    {
         string username=data.GetValues("username")[0];
         string password=data.GetValues("password")[0];
           string email=data.GetValues("email")[0];

        return Content(username + password + email);
    }
}

public class SampleViewModel {
    public int Id { get; set;}
    public string Name { get; set; }
}

public IHttpActionResult SampleActionMethod(SampleViewModel model) {
     if (!ModelState.IsValid) {
          return BadRequest();
     }
     var sampleDbModel = new SampleDatabaseModel() {
          FullName = model.Name,
          ProductId = model.Id,
          // ... some other properties ...
     };
     // ... Save the sampleDbModel ...
     return Ok(); // .. or Created ...
}