Программно шифруя файл конфигурации в.NET

Просто используйте библиотеку CloseMXL.Excel. Это легко и довольно быстро.

Класс

private DataTable getAllList()
        {
            string constr = ConfigurationManager.ConnectionStrings["RConnection"].ConnectionString;
            using (SqlConnection con = new SqlConnection(constr))
            {
                using (SqlCommand cmd = new SqlCommand("SELECT EmpId, gender, EmpName, pOnHold FROM Employee  WHERE EmpId= '"+ AnyVariable + "' ORDER BY EmpName"))
                {
                    using (SqlDataAdapter da = new SqlDataAdapter())
                    {
                        DataTable dt = new DataTable();
                        cmd.CommandType = CommandType.Text;
                        cmd.Connection = con;
                        da.SelectCommand = cmd;
                        da.Fill(dt);
                        dt.Columns[0].ColumnName = "Employee Id";
                        dt.Columns[1].ColumnName = "Gender";
                        dt.Columns[2].ColumnName = "Employee Name";
                        dt.Columns[3].ColumnName = "On Hold";

                        return dt;
                    }
                }
            }
        }

Затем другой метод, который получает набор данных

public DataSet getDataSetExportToExcel()
        {
            DataSet ds = new DataSet();
            DataTable dtEmp = new DataTable("CLOT List");
            dtEmp = getAllList();
             ds.Tables.Add(dtEmp);
             ds.Tables[0].TableName = "Employee"; //If you which to use Mutliple Tabs
             return ds;
          }

Теперь вы нажмите кнопку Click Событие

protected void btn_Export_Click(object sender, EventArgs e)
        {
            DataSet ds = getDataSetExportToExcel();

            using (XLWorkbook wb = new XLWorkbook())
            {
                wb.Worksheets.Add(ds);
                wb.Style.Alignment.Horizontal = XLAlignmentHorizontalValues.Center;
                wb.Style.Font.Bold = true;

                Response.Clear();
                Response.Buffer = true;
                Response.Charset = "";
                Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
                Response.AddHeader("content-disposition", "attachment;filename=EmployeeonHoldList.xlsx");

                using (MemoryStream MyMemoryStream = new MemoryStream())
                {
                    wb.SaveAs(MyMemoryStream);
                    MyMemoryStream.WriteTo(Response.OutputStream);

                    Response.Flush();
                    Response.End();
                }
            }
        }