private void btnAdd_Click(object sender, EventArgs e)
        {
            FrmProductEdit frm = new FrmProductEdit();

            frm.ShowDialog();
            RefreshData();
        }
        private void btnModify_Click(object sender, EventArgs e)
        {
            if (dataGridView1.SelectedRows.Count == 0)
            {
                return;
            }
            int            id  = (int)dataGridView1.SelectedRows[0].Cells[0].Value;
            FrmProductEdit frm = new FrmProductEdit();

            frm.Id = id;
            frm.ShowDialog();
            dataGridView1.InvalidateRow(dataGridView1.SelectedRows[0].Index);
        }