关于 windows服务 操作excel问题
下面是我的代码：请教高手指点下 我错误的地方实在不清楚了
  private void timer1_Tick(object sender, EventArgs e)
  {
  string cconnect_string = @"Data Source=ip,1433;Network Library = DBMSSOCN;Initial Catalog=hycar_ll;user id=sa;pwd=1;Persist Security Info = true";
  SqlConnection con = new SqlConnection(cconnect_string);
  try
  {
  con.Open();
  WriteLog("电信数据库链接成功！");
  }
  catch
  {
  WriteLog("电信数据库无法链接，请检查！");
  }
  string sql = "select * from mesge";
  SqlDataAdapter da = new SqlDataAdapter(sql, con);
  DataSet ds = new DataSet();
  da.Fill(ds, "类型");
  con.Close();
  string date = DateTime.Now.Date.ToString("yyyy-MM-dd");
  // MessageBox.Show(date);
  string time = DateTime.Now.Hour.ToString() + "-" + DateTime.Now.Minute.ToString();
  if (!Directory.Exists(@"d:\excel"))
  {
  Directory.CreateDirectory(@"d:\excel");
  WriteLog("正在创建路径：" + @"d:\excel");
  }
  if (File.Exists(@"d:\excel\" + @"\" + date.Trim() + ".xls"))
  {
  File.Delete(@"d:\excel\" + date.Trim() + ".xls");
  WriteLog(@"d:\excel\" + date.Trim() + ".xls");
  }
  string ss = @"d:\excel\" + date.Trim() + ".xls";
  //doExport(ds, ss.Trim());
  WriteLog(ss);
  /////最主要是程序到了这一步不执行了导出excel
  Microsoft.Office.Interop.Excel.Application excel = new Microsoft.Office.Interop.Excel.Application();
  WriteLog("1");
  if (excel == null)
  {
  WriteLog("你系统没有安装excel");
  timer1.Start();
  }
  else
  {
  WriteLog("系统安装excel");
  }
  try
  {
  WriteLog("尝试写入excel");
  int rowIndex = 1;
  int colIndex = 0;

  excel.Application.Workbooks.Add(true);
  Microsoft.Office.Interop.Excel.Workbook workbook = excel.Workbooks.Add(Microsoft.Office.Interop.Excel.XlWBATemplate.xlWBATWorksheet);
  Microsoft.Office.Interop.Excel.Worksheet worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Worksheets[1];
  Microsoft.Office.Interop.Excel.Range range;
  excel.Visible = false;
  //range = worksheet.get_Range(excel.Cells[2, 1], excel.Cells[rowNumber + 1, columnNumber]);
  System.Data.DataTable table = ds.Tables[0];
  foreach (DataColumn col in table.Columns)
  {
  colIndex++;
  excel.Cells[1, colIndex] = col.ColumnName;
  }
  foreach (DataRow row in table.Rows)
  {
  rowIndex++;
  colIndex = 0;
  foreach (DataColum