[HttpPost]// thuc hien dang nhap
        public ActionResult VerifyLogin(User user)
        {
            // kiem tra du lieu nhap
            if (ModelState.IsValid)
            {
                // truy van csdl
                string uid = null;
                using (var _context = new DA_QLTMDTEntities())
                {
                    // query id tu email va password de kiem tra dang nhap
                    try
                    {
                        var id = (from u in _context.Users where u.Email == user.Email && u.Password == user.Password select u).FirstOrDefault();
                        uid = id.ToString();
                    }
                    catch { }
                }

                if (uid != null)
                {
                    mydb.closeConnection();
                    return(View("LoginSuccess"));
                }
                else
                {
                    mydb.closeConnection();
                    return(View("Error"));
                }
            }
            return(View("Login"));
        }
        public string GetUserIDbyEmail(string email)
        {
            string uid = default;

            using (var _context = new DA_QLTMDTEntities())
            {
                // query id tu email va password de kiem tra dang nhap
                try
                {
                    var id = (from u in _context.Users where u.Email == email select u).FirstOrDefault();
                    uid = id.ToString();
                }
                catch { }
            }
            return(uid);
        }
        [HttpPost] // thuc hien dang ki
        public ActionResult RegisterUser(User user)
        {
            // lay id cua user tu email
            string uid = null;

            // kiem tra du lieu nhap
            if (ModelState.IsValid)
            {
                using (var _context = new DA_QLTMDTEntities())
                {
                    try
                    {
                        var id = (from u in _context.Users where u.Email == user.Email select u).FirstOrDefault();
                        uid = id.ToString();
                    }
                    catch { }
                    if (uid == null)
                    {
                        //Response.Write("<script>alert('Data inserted successfully')</script>");
                        try
                        {
                            mydb.openConnection();
                            SqlCommand command = new SqlCommand("INSERT INTO Users (Name,Email,Password) Values( '" + user.Name + "', '" + user.Email + "','" + user.Password + "')", mydb.getConnection);
                            command.ExecuteNonQuery();
                            mydb.closeConnection();
                            Response.Write("<script>alert('Data inserted successfully')</script>");
                            return(View("LoginSuccess"));
                        }
                        catch
                        {
                            return(View());
                        }
                    }
                    else
                    {
                        // Response.Write("<script>alert('Data inserted successfully')</script>");
                        return(View("Error"));
                    }
                }
            }
            return(View("Register"));
        }