iTextSharp Pdftable问题

Question

我在使用iTextSharp dll从Windows窗体生成pdf时遇到问题。我在数据集中一次填充超过70条记录，并通过循环将其绑定到新表（pdfptable）。但是它说对象引用没有设置为对象的实例。当我将行数减少到68时，它可以正常工作。经过分析，我发现表格无法沿多页分割。

我正在使用以下代码。请帮忙

            float[] widths1 = new float[] { 1f, 2f,1f,1f,1f,1f,1f};

            PdfPTable grd = new PdfPTable(GrdAnoSecList.Columns.Count);
            grd.SetWidths(widths1);

            for (int i = 0; i < GrdAnoSecList.Columns.Count; i++)
            {
                PdfPCell ph;
                if (Convert.ToString(GrdAnoSecList.Columns[i].HeaderText) == "Job Name")
                {
                    ph = new PdfPCell(new Phrase(GrdAnoSecList.Columns[i].HeaderText, grdfontHdr));
                    ph.BackgroundColor = new iTextSharp.text.Color(240, 240, 240);
                    ph.BorderWidthTop = 0;
                    ph.BorderWidthRight = 0;
                    ph.HorizontalAlignment = 1;
                }
                else
                {
                     ph= new PdfPCell(new Phrase(GrdAnoSecList.Columns[i].HeaderText, grdfontHdr));
                     ph.BackgroundColor = new iTextSharp.text.Color(240, 240, 240);
                     ph.BorderWidthTop = 0;
                     ph.BorderWidthRight = 0;
                     ph.HorizontalAlignment = 1;
                     //ph.Width = 100f;
                }

                grd.AddCell(ph);
            }
            int ct = 0;
            foreach (DataGridViewRow row in GrdAnoSecList.Rows)
            {
                foreach (DataGridViewCell cell in row.Cells)
                {
                    ct++;
                    PdfPCell ph2;
                    if (Convert.ToString(cell.Value) == "Total")
                    {
                        ph2 = new PdfPCell(new Phrase(cell.Value.ToString(), grdfontHdr));
                    }
                    else
                    {
                        ph2 = new PdfPCell(new Phrase(cell.Value.ToString(), myfont));
                    }
                    if (cell.ValueType == typeof(decimal) || cell.ValueType == typeof(Int32))
                    {
                        ph2.HorizontalAlignment = 2;
                    }
                    else if (cell.ColumnIndex == 1 && Convert.ToString(cell.Value) != "Total")
                    {
                        ph2.HorizontalAlignment = 0;
                    }
                    else
                    {
                        ph2.HorizontalAlignment = 1;
                    }

                    grd.AddCell(ph2);

                }
            }

            PdfPCell cellAmountText1 = new PdfPCell(new PdfPTable(grd));
            cellAmountText1.Colspan = 6;
            table.AddCell(cellAmountText1);