After login only user should access other pages

I can access index page without login i want that user should login first after that index page could access.

LoginController

public ActionResult Index(login LgnUsr)
{
    bool Isvalid = objCon.UserMasters.Any(x => x.MobileNo == LgnUsr.MobileNo && x.EmailVerification == true &&
    x.Password == LgnUsr.Password);
    var Det = objCon.UserMasters.Where(x => x.MobileNo == LgnUsr.MobileNo &&
    x.Password == LgnUsr.Password).ToList<UserMaster>();
    //if (Det.Find()) 
    if (Det.Count > 0)
    {
        if (Det.FirstOrDefault().EmailVerification == false)
        {
            var GenarateUserVerificationLink = "/Register/UserVerification/" + Det.FirstOrDefault().ActivetionCode;
            var link = Request.Url.AbsoluteUri.Replace(Request.Url.PathAndQuery, GenarateUserVerificationLink);
            // TempData["ErrorMSG"] = "Email Verification in Pending.";
            ModelState.AddModelError("", "Email Verification in Pending !");
            ViewBag.link = link;
            return View();
        }
    }
    if (Isvalid)
    {
        int timeout = LgnUsr.Rememberme ? 60 : 30; // Timeout in minutes, 60 = 1 hour. 
        var ticket = new FormsAuthenticationTicket(Det.FirstOrDefault().Email, false, timeout);
        string encrypted = FormsAuthentication.Encrypt(ticket);
        var cookie = new HttpCookie(FormsAuthentication.FormsCookieName, encrypted);
        cookie.Expires = System.DateTime.Now.AddMinutes(timeout);
        cookie.HttpOnly = true;
        Response.Cookies.Add(cookie);
        FormsAuthentication.SetAuthCookie(Det.FirstOrDefault().Email, true);
        Session["UserName"] = Det.FirstOrDefault().Email;
        Session["FName"] = Det.FirstOrDefault().UserFullName;
        Session["LName"] = Det.FirstOrDefault().LastName;
        Session["UserId"] = Det.FirstOrDefault().UserId;
        Session["Code"] = Det.FirstOrDefault().ActivetionCode;
        return RedirectToAction("Dashboard", "Home");
    }
    else
    {
        ModelState.AddModelError("", "Username or Password is Invalid !");
        //TempData["ErrorMSG"] = "Username or Password is Invalid !";
        // ModelState.Clear();
    }
    return View();
}

Web.config

<authentication mode="Forms">
    <forms loginUrl="~/Login/Index" timeout="2880" />
</authentication>