Blank PDF generated when exporting ASP.Net Chart to PDF using iTextSharp

After using the code from your article, an empty pdf file is opening...can you please let me know where I am doing mistake.

My chart binding code is

private void Createchart1(DataTable dt, Chart _chart)
        {
            SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                try
                {
                    if (dt.Rows.Count > 0)
                    {
                        int s = 0;
                        foreach (DataRow dr in dt.Rows)
                        {
                            if (!string.IsNullOrEmpty(dr["Reply"].ToString()))
                            {
                                _chart.Series["Series1"].ChartType = SeriesChartType.Pie;

                                _chart.Series["Series1"].Points.AddXY(dr["Reply"].ToString(), dr["Count"].ToString());
                                _chart.Series["Series1"].ResetIsValueShownAsLabel();
                                _chart.Series["Series1"].Points[s].Label = dr["Reply"].ToString() + "  -  " + dr["Count"].ToString();
                                if (dr["Reply"].ToString().Contains("Not Sent"))
                                {
                                    //_chart.Series["Series1"].Points[s].Color = System.Drawing.ColorTranslator.FromHtml("#CC6600");
                                    //_chart.Series["Series1"].Points[s].Color = System.Drawing.Color.Blue;
                                    _chart.Series["Series1"].Points[s].Color = System.Drawing.ColorTranslator.FromHtml("#0080FF");

                                }
                                else
                                {
                                   // _chart.Series["Series1"].Points[s].Color = System.Drawing.ColorTranslator.FromHtml("#663300");
                                   // _chart.Series["Series1"].Points[s].Color = System.Drawing.Color.Green;
                                    _chart.Series["Series1"].Points[s].Color = System.Drawing.ColorTranslator.FromHtml("#38E07C");
                                }
                                _chart.Visible = true;
                                _chart.Series["Series1"].Points[s].LabelForeColor = System.Drawing.Color.White;
                                _chart.Legends.Clear();
                                _chart.ChartAreas[0].AxisX.IsLabelAutoFit = false;
                                _chart.ChartAreas[0].AxisX.LabelStyle.Angle = -90;
                                s++;
                            }
                        }

                    }
                    else
                    {
                        _chart.Visible = false;
                    }
                }
                catch (Exception ex)
                {
                    lblchartmsg.ForeColor = System.Drawing.Color.Red;
                    lblchartmsg.Text = ex.Message.ToString();
                }
            });
        }