How to create an Excel 2003 (.XLS) file with password protection without Excel installed using C #?

Question

In C #, how can I create a PASSWORD IS PROTECTED (the user must enter a password to open the file at all) .XLS file without installing Excel (therefore, not Interop)? NPOI and ExcelLibrary look promising (because they are free!), But I can not find anywhere, regardless of whether they really support password protection. I cannot use EPPlus as it deals only with .XSLX files and not with my required .XLS.

In addition, I would like to use an array to populate the data, not a cell by cell. Here is what I did for this when I used Interop in the past, which was infinitely faster than the cell by cell method:

object[,] data = new object[length, ColumnHeaders.Count];
...
dynamic rg = excelApp.Sheets[p].Range[excelApp.Sheets[p].Cells[top, left], excelApp.Sheets[p].Cells[bottom, right]];
rg.Value = data;

Answer 1

Export Code

 public void ExportNewPatientsToExcel()
    {
        logger.Info("New Patients :: export to excel");
        string fileDirectory = string.Empty;

        if (Session[Constants.SESSION_FILE_DIRECTORY] != null)
            fileDirectory = Session[Constants.SESSION_FILE_DIRECTORY].ToString();
        else
        {
            logger.Error("New Patients::File Cache folder is not set.");
            Response.Redirect(Constants.PAGE_ERROR);
        }

        HttpContext context = HttpContext.Current;

        try
        {           
            string xsltFileName = Context.Server.MapPath(Constants.NEW_PATIENTS_XSLT_FILE_NAME);
            PatientCollection patientCollection = PatientBAO.GetNewPatients(ShowAllPatient);

            if (patientCollection.Count > 0 && patientCollection != null)
            {
                string fileName = PatientBAO.GenerateNewPatientsAsExcel(fileDirectory, xsltFileName, patientCollection);
                logger.Info("New Patients Excel version saved name :" + fileName);
                string fileNamePart = fileName.Substring(fileName.LastIndexOf("\\") + 1);
                fileNamePart = fileNamePart.Substring(fileNamePart.IndexOf("_") + 1);//added to remove session id from file name

                context.Items.Add(Constants.ENABLE_CACHE_SZ, Constants.ENABLE_CACHE);
                context.Response.ClearContent();
                context.Response.AddHeader("Content-Disposition", "attachment;filename=" + fileNamePart);
                context.Response.ContentType = "application/octet-stream";
                context.Response.TransmitFile(fileName);                
            }
            else
            {
                ShowPopUp(Resources.Patient.RecordNotFoundToExportExcel);
                logger.Error("New patients data not found for export to excel.");
            }
        }
        catch (Exception exc)
        {
            logger.ErrorException("Error occured while export patient details to excel.", exc);
        }
        finally
        {
            //HttpContext.Current.ApplicationInstance.CompleteRequest();
            context.Response.End();
        }
    }

The part of the password that is working on.

Answer 2

Check out the sample code for the sauce from: http://forums.asp.net/t/1831409.aspx

You can also populate data using a dataset rather than cell by cell.