private string Mapn()
        {
            DataTable dt = bll.LoadPN();

            if (dt.Rows.Count == 0)
            {
                return("PN01");
            }
            else
            {
                string a     = dt.Rows[0][0].ToString();
                int    mamax = int.Parse(a.Substring(2, a.Length - 2));
                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    string b  = dt.Rows[i][0].ToString();
                    int    ma = int.Parse(b.Substring(2, b.Length - 2));
                    if (ma > mamax)
                    {
                        mamax = ma;
                    }
                }
                return("PN0" + (mamax + 1).ToString());
            }
        }