private void btnLamMoi_Click(object sender, EventArgs e)
{
dgvSP.ClearSelection();
string matieptheo = spBUS.MaSPTiepTheo();
SPChon = null;
txtMaSP.Text = matieptheo;
txtTenSP.Text = null;
txtGiaBan.Text = null;
txtSLT.Text = null;
dtpHSD.Value = DateTime.Now;
cboLoaiSP.SelectedIndex = 0;
cboLoaiNCC.SelectedIndex = 0;
chkTT.Checked = true;
pboHASP.Image = null;
}