/// <summary>
        /// Print to pdf format
        /// </summary>
        private void btn_Print_Click(object sender, EventArgs e)
        {
                try
                {
                    Random rnd = new Random();
                    int rndNum = rnd.Next(1, 100);
                    string fileName = Utils.tableName + "" + rndNum + ".pdf";
                    string fileHeader = "DANH SÁCH " + Utils.tableName + "";

                    // export pdf to print
                    adapter.Fill(db);
                    dgvShowInf.DataSource = db;
                    dgvShowInf.Columns["rowguid"].Visible = false;
                    Utils.ExportDataTableToPdf(db, @".\document\" + fileName+"", fileHeader);
                    System.Diagnostics.Process.Start(@".\document\" + fileName);
                    WindowState = FormWindowState.Minimized;
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "In danh sách thất bại");
                }
        }

 // Export dtb to pdf for print
       public static void ExportDataTableToPdf(DataTable dtblTable, String strPdfPath, string strHeader)
       {
            System.IO.FileStream fs = new FileStream(strPdfPath, FileMode.Create, FileAccess.Write, FileShare.None);
            Document document = new Document();
            document.SetPageSize(PageSize.A4);
            PdfWriter writer = PdfWriter.GetInstance(document, fs);
            document.Open();

            //Report Header
            BaseFont bfntHead = BaseFont.CreateFont(BaseFont.TIMES_ROMAN, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            Font fntHead = new Font(bfntHead, 16, 1, BaseColor.BLACK);
            Paragraph prgHeading = new Paragraph();
            prgHeading.Alignment = Element.ALIGN_CENTER;
            prgHeading.Add(new Chunk(strHeader.ToUpper(), fntHead));
            document.Add(prgHeading);

            //Author
            Paragraph prgAuthor = new Paragraph();
            BaseFont btnAuthor = BaseFont.CreateFont(BaseFont.TIMES_ROMAN, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            Font fntAuthor = new Font(btnAuthor, 8, 2, BaseColor.GRAY);
            prgAuthor.Alignment = Element.ALIGN_RIGHT;

            prgAuthor.Add(new Chunk("Khoa : " + Utils.khoa.ToString() + "", fntAuthor));
            prgAuthor.Add(new Chunk("\nNgày : " + DateTime.Now.ToShortDateString(), fntAuthor));
            document.Add(prgAuthor);

            ////Add a line seperation
            Paragraph p = new Paragraph(new Chunk(new iTextSharp.text.pdf.draw.LineSeparator(0.0F, 100.0F, BaseColor.BLACK, Element.ALIGN_LEFT, 1)));
            document.Add(p);

            //Add line break
            document.Add(new Chunk("\n", fntHead));

            //Write the table
            PdfPTable table = new PdfPTable(dtblTable.Columns.Count);

            //Table header
            BaseFont btnColumnHeader = BaseFont.CreateFont(BaseFont.TIMES_ROMAN, BaseFont.CP1252, BaseFont.NOT_EMBEDDED);
            Font fntColumnHeader = new Font(btnColumnHeader, 10, 1, BaseColor.WHITE);
            for (int i = 0; i < dtblTable.Columns.Count; i++)
            {
                PdfPCell cell = new PdfPCell();
                cell.BackgroundColor = BaseColor.GRAY;
                cell.AddElement(new Chunk(dtblTable.Columns[i].ColumnName.ToUpper(), fntColumnHeader));
                table.AddCell(cell);
            }
            //table Data
            for (int i = 0; i < dtblTable.Rows.Count; i++)
            {
                for (int j = 0; j < dtblTable.Columns.Count; j++)
                {
                    table.AddCell(dtblTable.Rows[i][j].ToString());
                }
            }
            document.Add(table);
            document.Close();
            writer.Close();
            fs.Close();
        }