private async void btnXoa_Click(object sender, EventArgs e)
{
btnXoa.Enabled = false;
btnHuyBo.Visible = false;
btnLamMoi.Visible = true;
object tietHoc = await apis.DeleteTietHoc(typingTiet.id);
await LoadData();
btnNhapLai.Enabled = true;
btnLamMoi.Visible = true;
btnThem.Enabled = true;
btnCapNhat.Enabled = false;
isEditting = false;
cbxXem.Enabled = true;
gridTietHoc.Enabled = true;
dateNgay.EditValue = typingTiet.ngay;
cbxTietHoc.Text = typingTiet.tiet;
txtBaiBuoi.Text = typingTiet.bai;
cbxHinhThuc.Text = typingTiet.hinhThuc;
txtGiangVien.Text = typingTiet.giangViens;
txtDiaDiem.Text = typingTiet.diaDiem;
txtMonHoc.Text = typingTiet.mon != null ? typingTiet.mon.ma : "";
lblLoiMon.Visible = false;
}