DataSet mDSData = new DataSet();
mDSData.Tables.Add("myTable");
mDSData.Tables["myTable"].Columns.Add("ID");
mDSData.Tables["myTable"].Columns.Add("Name");
mDSData.Tables["myTable"].Columns.Add("PassWord");
for (int i = 0; i < 10; i++)
{
  DataRow dr = mDSData.Tables["myTable"].NewRow();
  dr["ID"] = i;
  dr["Name"] = i;
  dr["PassWord"] = i;
  mDSData.Tables["myTable"].Rows.Add(dr);
}
SaveFileDialog dialog1 = new SaveFileDialog();
dialog1.AddExtension = true;
dialog1.CheckPathExists = true;
dialog1.Filter = "Excel Workbooks (*.xls) | *.xls";
dialog1.OverwritePrompt = true;
dialog1.Title = "Save Excel Formatted Report";
if (dialog1.ShowDialog() == DialogResult.OK)
{
  int num2 = 0;
  int num3 = mDSData.Tables[0].Rows.Count + 1;
  int num1 = mDSData.Tables[0].Columns.Count;
  num2 = 0;
  string text1 = dialog1.FileName;
  if (File.Exists(text1))
  {
    File.Delete(text1);
  }
  StreamWriter writer1 = new StreamWriter(text1, false);
  StreamWriter writer2 = writer1;
  writer2.WriteLine("<?xml version=\"1.0\"?>");
  writer2.WriteLine("<?mso-application progid=\"Excel.Sheet\"?>");
  writer2.WriteLine("<Workbook xmlns=\"urn:schemas-microsoft-com:office:spreadsheet\"");
  writer2.WriteLine(" xmlns:o=\"urn:schemas-microsoft-com:office:office\"");
  writer2.WriteLine(" xmlns:x=\"urn:schemas-microsoft-com:office:excel\"");
  writer2.WriteLine(" xmlns:ss=\"urn:schemas-microsoft-com:office:spreadsheet\"");
  writer2.WriteLine(" xmlns:html=\"http://www.w3.org/TR/REC-html40\">");
  writer2.WriteLine(" <DocumentProperties xmlns=\"urn:schemas-microsoft-com:office:office\">");
  writer2.WriteLine(" <Author>Automated Report Generator Example</Author>");
  writer2.WriteLine(string.Format(" <Created>{0}T{1}Z</Created>", DateTime.Now.ToString("yyyy-mm-dd"), DateTime.Now.ToString("HH:MM:SS")));
  writer2.WriteLine(" <Company>Your Company Here</Company>");
  writer2.WriteLine(" <Version>11.6408</Version>");
  writer2.WriteLine(" </DocumentProperties>");
  writer2.WriteLine(" <ExcelWorkbook xmlns=\"urn:schemas-microsoft-com:office:excel\">");
  writer2.WriteLine(" <WindowHeight>8955</WindowHeight>");
  writer2.WriteLine(" <WindowWidth>11355</WindowWidth>");
  writer2.WriteLine(" <WindowTopX>480</WindowTopX>");
  writer2.WriteLine(" <WindowTopY>15</WindowTopY>");
  writer2.WriteLine(" <ProtectStructure>False</ProtectStructure>");
  writer2.WriteLine(" <ProtectWindows>False</ProtectWindows>");
  writer2.WriteLine(" </ExcelWorkbook>");
  writer2.WriteLine(" <Styles>");
  writer2.WriteLine(" <Style ss:ID=\"Default\" ss:Name=\"Normal\">");
  writer2.WriteLine("  <Alignment ss:Vertical=\"Bottom\"/>");
  writer2.WriteLine("  <Borders/>");
  writer2.WriteLine("  <Font/>");
  writer2.WriteLine("  <Interior/>");
  writer2.WriteLine("  <Protection/>");
  writer2.WriteLine(" </Style>");
  writer2.WriteLine(" <Style ss:ID=\"s21\">");
  writer2.WriteLine("  <Alignment ss:Vertical=\"Bottom\" ss:WrapText=\"1\"/>");
  writer2.WriteLine(" </Style>");
  writer2.WriteLine(" </Styles>");
  writer2.WriteLine(" <Worksheet ss:Name=\"MyReport\">");
  writer2.WriteLine(string.Format(" <Table ss:ExpandedColumnCount=\"{0}\" ss:ExpandedRowCount=\"{1}\" x:FullColumns=\"1\"", num1.ToString(), num3.ToString()));
  writer2.WriteLine("  x:FullRows=\"1\">");
  foreach (DataRow row1 in mDSData.Tables[0].Rows)
  {
    writer2.WriteLine("<Row>");
    for (num2 = 0; num2 != num1; num2++)
    {
      writer2.Write("<Cell ss:StyleID=\"s21\"><Data ss:Type=\"String\">");
      writer2.Write(row1[num2].ToString());
      writer2.WriteLine("</Data></Cell>");
    }
    writer2.WriteLine("</Row>");
  }
  writer2.WriteLine(" </Table>");
  writer2.WriteLine(" <WorksheetOptions xmlns=\"urn:schemas-microsoft-com:office:excel\">");
  writer2.WriteLine("  <Selected/>");
  writer2.WriteLine("  <Panes>");
  writer2.WriteLine("  <Pane>");
  writer2.WriteLine("   <Number>3</Number>");
  writer2.WriteLine("   <ActiveRow>1</ActiveRow>");
  writer2.WriteLine("  </Pane>");
  writer2.WriteLine("  </Panes>");
  writer2.WriteLine("  <ProtectObjects>False</ProtectObjects>");
  writer2.WriteLine("  <ProtectScenarios>False</ProtectScenarios>");
  writer2.WriteLine(" </WorksheetOptions>");
  writer2.WriteLine(" </Worksheet>");
  writer2.WriteLine(" <Worksheet ss:Name=\"Sheet2\">");
  writer2.WriteLine(" <WorksheetOptions xmlns=\"urn:schemas-microsoft-com:office:excel\">");
  writer2.WriteLine("  <ProtectObjects>False</ProtectObjects>");
  writer2.WriteLine("  <ProtectScenarios>False</ProtectScenarios>");
  writer2.WriteLine(" </WorksheetOptions>");
  writer2.WriteLine(" </Worksheet>");
  writer2.WriteLine(" <Worksheet ss:Name=\"Sheet3\">");
  writer2.WriteLine(" <WorksheetOptions xmlns=\"urn:schemas-microsoft-com:office:excel\">");
  writer2.WriteLine("  <ProtectObjects>False</ProtectObjects>");
  writer2.WriteLine("  <ProtectScenarios>False</ProtectScenarios>");
  writer2.WriteLine(" </WorksheetOptions>");
  writer2.WriteLine(" </Worksheet>");
  writer2.WriteLine("</Workbook>");
  writer2 = null;
  writer1.Close();
  MessageBox.Show("Report Created", "Success", MessageBoxButtons.OK, MessageBoxIcon.Asterisk);
}