Export all Files in PDF Format at a Time using C#

public void updatestaus(string F)
{
    sc.Close();
    sc.Open();
    SqlCommand cmd = new SqlCommand("update BOND_REG set status='P' where fliono='" + F + "'", sc);
    cmd.ExecuteNonQuery();
    sc.Close();
}
protected void Button2_Click(object sender, EventArgs e)
{
    sc.Open();
    SqlCommand cmd = new SqlCommand("select Fliono from BOND_REG where status='A'", sc);
    SqlDataReader SDR = cmd.ExecuteReader();
    while (SDR.Read() == true) {
        string St = SDR.GetValue(0).ToString();
        //SDR.Close();
        // SDR.Dispose();
        fileexport(St);
        updatestaus(St);
}
SDR.Close();
sc.Close();
}
public void fileexport(string st1)
{
    // SDR.Close();
    SqlCommand cmd1 = new SqlCommand("select * from BOND_REG where status='A' and Fliono='" + st1 + "'", sc);
    SqlDataAdapter da = new SqlDataAdapter();
    da.SelectCommand = cmd1;
    DataTable datatable = new DataTable();
    da.Fill(datatable);
    ReportDocument crystalReport = new ReportDocument();
    crystalReport.Load(Server.MapPath("~/bond.rpt"));
    crystalReport.SetDataSource(datatable);
    ExportOptions rptExportOption;
    DiskFileDestinationOptions rptFileDestOption = new DiskFileDestinationOptions();
    PdfRtfWordFormatOptions rptFormatOption = new PdfRtfWordFormatOptions();
    string reportFileName = @
    "C:\pdfd\ st1.pdf";
    rptFileDestOption.DiskFileName = reportFileName;
    rptExportOption = crystalReport.ExportOptions;
    {
        rptExportOption.ExportDestinationType = ExportDestinationType.DiskFile;
        rptExportOption.ExportFormatType = ExportFormatType.PortableDocFormat;
        rptExportOption.ExportDestinationOptions = rptFileDestOption;
        rptExportOption.ExportFormatOptions = rptFormatOption;
    }
    crystalReport.Export();
}