private void set_initial_form_load()
{
//m_lbl_nam_tinh_thue.Text = DateTime.Now.Year.ToString();
m_dat_tu_thang.EditValue = DateTime.Now.AddMonths(-DateTime.Now.Month+ 1).AddDays(-DateTime.Now.Day + 1).Date;
m_dat_den_thang.EditValue = DateTime.Now.Date;
load_data_to_grid();
}