Db not found in MVC 4

public JsonResult UserLogin(Login d)
      {

          List<sp_customer_login_Result> Skill = new List<sp_customer_login_Result>();
          {
              Skill = db.sp_customer_login(d.Email.ToString()).ToList();

          }
          return new JsonResult { Data = Skill, JsonRequestBehavior = JsonRequestBehavior.AllowGet };

      }
  }