private void tenloaiclick(object sender, EventArgs e)
        {
            database db = new database();
            LoaiHoa  l  = new LoaiHoa {
                Tenloai = txttenloai.Text
            };

            if (db.Insertloai(l) == true)
            {
                DisplayAlert("Notify", "Success", "Ok");
            }
            else
            {
                DisplayAlert("Notify", "False", "Ok");
            }
        }