How to Read the Uploaded Excel File using NPOI with out storing in the server or in the Project

Question

My sample Code is below using the NPOI.dll. I can read the EXCEL File (i.e. Excel would be stored in the system like D:/Jamal/Test.xls. Then the dll is easily reading the content, but I need to read the uploaded Excel file without storing it in any place before.The HTTPPOSTEDFILEBASE excelfile has the value for the Excel file but I need to know how to read it using NPOI dlls

public List<string> SendInvitesExcelFile1(List<String> CorrectMailIDs,
                                     ListInvites Invites, HttpPostedFileBase excelfile)
{
        List<string> mailids = new List<string>();
        //string filename = (excelfile.FileName).ToString();
        HSSFWorkbook hssfwb;
    //   using (FileStream file = new FileStream(@"D:\test.xls", FileMode.Open, FileAccess.Read))

         using (FileStream file = new FileStream(excelFile.FileName, FileMode.Open, FileAccess.Read))
        { 
             hssfwb = new HSSFWorkbook(file);
        }

        Sheet sheet = hssfwb.GetSheet("sheet1");
        for (int row = 0; row <= sheet.LastRowNum; row++)
        {
            if (sheet.GetRow(row) != null) //null is when the row only contains empty cells 
            {
                mailids.Add(sheet.GetRow(row).GetCell(0).ToString());
            }
        }
        return mailids;

Answer 1

I came across the same problem and I solved it using Inpustream. I am pasting the code for your reference.

[HttpPost]
    public DataTable PostValues(HttpPostedFileBase file)
    {
       ISheet sheet;
       string filename = Path.GetFileName(Server.MapPath(file.FileName));
       var fileExt = Path.GetExtension(filename);
       if (fileExt == ".xls")
         {
          HSSFWorkbook hssfwb = new HSSFWorkbook(file.InputStream); 
          sheet = hssfwb.GetSheetAt(0);
          }
        else             
          {
          XSSFWorkbook hssfwb = new XSSFWorkbook(file.InputStream); 
          sheet = hssfwb.GetSheetAt(0);
          }

       DataTable table = new DataTable();
       IRow headerRow = sheet.GetRow(0);
       int cellCount = headerRow.LastCellNum;
       for (int i = headerRow.FirstCellNum; i < cellCount; i++)
       {
        DataColumn column = new DataColumn(headerRow.GetCell(i).StringCellValue);
        table.Columns.Add(column);
        }
       int rowCount = sheet.LastRowNum;
       for (int i = (sheet.FirstRowNum); i < sheet.LastRowNum; i++)
        {
         IRow row = sheet.GetRow(i);
        DataRow dataRow = table.NewRow();
         for (int j = row.FirstCellNum; j < cellCount; j++)
        {
          if (row.GetCell(j) != null)
            {
            dataRow[j] = row.GetCell(j).ToString();
            }
        }
    table.Rows.Add(dataRow);
                        }
      return table;
        }

Answer 2

You can use a MemoryStream as well, so you should be able to get the byte array repsonse and open the spreadsheet. I'm unsure if the WorkbookFactory will detect the file type from the MemoryStream, so you may need to instruct the users to use the format that you require.