How to get data from SQL server express 2014 in ASP.NET using linq?

See more:

SQL-Server

LINQ

ASP.NET5

Problem:
I'm trying to get data from sql server using linq and then verifying it. But it not getting data. I also write a function for sending data into sql server that store data.

My Controller
:

private DB db = new DB(); //Database context

public ActionResult Index()
{
    return View();
}

[HttpGet]
public ActionResult Sign()
{
    return View();
}

[HttpPost]
public ActionResult Sign(Login l)
{
    var user = db.Logins.Where(s => s.Username == l.Username && s.Password == l.Password).FirstOrDefault();

    return RedirectToAction("check","Home");


}

What I have tried:

The main problem is that sign funtion(httppost) not getting data from sql server?