How to pass string value in controller

public ActionResult Login(string UserId)
    {
       // string mail = Decrypt(UserId);
        return View();
    }
    [HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult Login(UserProfile objUser)
    {

        //string EncryptedID = Decrypt(objUser.UserId);
        if (ModelState.IsValid)
        {
            using (DBEntities db = new DBEntities())
            {
                var obj = db.UserProfiles.Where(a => a.UserName.Equals(objUser.UserName) && a.Password.Equals(objUser.Password)).FirstOrDefault();
                if (obj != null)
                {
                    Session["UserId"] = obj.UserId.ToString();
                    Session["UserName"] = obj.UserName.ToString();
                    return RedirectToAction("UserDashBoard");
                }
            }