private async void Cart_Click1(object sender, EventArgs e)
        {
            myAPI = RestService.For <IMyAPI>("https://goldenspa.azurewebsites.net");
            var idCustomer = await myAPI.GetIdCustomer("0123456789");

            string cus = idCustomer.Substring(4, idCustomer.Length - 6);

            var List_Cart = await myAPI.GetCarts();

            int max = int.Parse(List_Cart[0].MaGioHang);

            for (int i = 1; i < List_Cart.Count; i++)
            {
                if (max < int.Parse(List_Cart[i].MaGioHang))
                {
                    max = int.Parse(List_Cart[i].MaGioHang);
                }
            }
            max++;
            Cart cartt = new Cart();

            cartt.MaGioHang = max.ToString();
            cartt.MaKh      = idCustomer.Substring(2, idCustomer.Length - 4);
            if (Intent.GetStringExtra("ServiceName") == null)
            {
                cartt.MaCombo = Intent.GetStringExtra("ServiceId");
            }
            else
            {
                cartt.MaDv = Intent.GetStringExtra("ServiceId");
            }
            var results = await myAPI.PostGioHang(cartt);

            Toast.MakeText(this, results, ToastLength.Short).Show();
        }