Develop Reference

Parsing xlsx files with unity

I use the following code to parse an XLSX file.
private IExcelDataReader GetExcelDataReaderForFile(string filePath)
{
FileStream stream = File.Open(filePath, FileMode.Open, FileAccess.Read);
// Create the excel data reader
IExcelDataReader excelReader;
excelReader = ExcelReaderFactory.CreateOpenXmlReader(stream);
// Close the stream
stream.Close();
// First row are columns names
excelReader.IsFirstRowAsColumnNames = true;
return excelReader;
}
Im running this code on my android. The path is subjective to Application.persistentDataPath. The problem here is that Im getting the following strange error,
Access to the path "/tmp" is denied.
How do I sort it out? or is there any other ways to parse xlsx files in Android?

You are requesting a file/directory at the root of the drive.
You should use ./tmp (notice the .) or if you insist Application.persistentDataPath + "/tmp"

NPOI - After saving to file corrupts .xlsx workbook

I used this code to write to an exciting excel file. After writing the file, when I open the file manually it is corrupted. I am using NPOI binary 2.3.0.0 Please tell how to avoid excel getting corrupted.
[Authorize]
public void ExportUsers()
{
var path = Server.MapPath(#"~\Content\ExportTemplates\") + "sample.xlsx";
FileStream sw = new FileStream(path, FileMode.Open, FileAccess.Read);
IWorkbook workbook = WorkbookFactory.Create(sw);
ISheet sheet = workbook.GetSheetAt(0);
IRow row = sheet.GetRow(12);
ICell cell = row.CreateCell(row.LastCellNum);
cell.SetCellValue("test");
workbook.CreateSheet("Ripon");
sw.Close();
using (var exportData = new MemoryStream())
{
workbook.Write(exportData);
string saveAsFileName = string.Format("Export-{0:d}.xls", DateTime.Now).Replace("/", "-");
System.Web.HttpContext.Current.Response.ContentType = "application/vnd.ms-excel";
System.Web.HttpContext.Current.Response.AddHeader("Content-Disposition", string.Format("attachment;filename={0}", saveAsFileName));
System.Web.HttpContext.Current.Response.Clear();
System.Web.HttpContext.Current.Response.BinaryWrite(exportData.GetBuffer());
System.Web.HttpContext.Current.Response.End();
}
}
New file is created but corrupted. I've seen people say this is fixed in version 2.0.6, but still not working for me

There are several problems going on here.
First, you are starting with an .xlsx file but then changing the download file extension to .xls. .xls and .xlsx are not the same file format; the former is a binary format, while the latter is a zipped XML format. If you save the file with the wrong extension, then Excel will report the file as corrupted when it is opened.
Second, you are using the wrong method to get the data from the MemoryStream. GetBuffer will return the entire allocated internal buffer array, which will include any unused bytes that are beyond the end of the data if the buffer is not completely full. The extra null bytes will cause the downloaded file to be corrupted. If you want to get just the data in the buffer then you should use ToArray instead.
Third, it looks like you are using the ASP.NET MVC framework (based on the presence of the [Authorize] attribute on your method) but you are directly manipulating the current response instead of using the controller's built-in File method for returning a downloadable file. I would recommend using the built-in methods where possible, as it will make your code much cleaner.
Here is the corrected code:
[Authorize]
public ActionResult ExportUsers()
{
var path = Server.MapPath(#"~\Content\ExportTemplates\") + "sample.xlsx";
FileStream sw = new FileStream(path, FileMode.Open, FileAccess.Read);
IWorkbook workbook = WorkbookFactory.Create(sw);
ISheet sheet = workbook.GetSheetAt(0);
IRow row = sheet.GetRow(12);
ICell cell = row.CreateCell(row.LastCellNum);
cell.SetCellValue("test");
workbook.CreateSheet("Ripon");
sw.Close();
var exportData = new MemoryStream();
workbook.Write(exportData);
exportData.Seek(0, SeekOrigin.Begin); // reset stream to beginning so it can be read
string saveAsFileName = string.Format("Export-{0:d}.xlsx", DateTime.Now).Replace("/", "-");
return File(exportData, "application/vnd.ms-excel", saveAsFileName);
}

Problematic corruption of .xlsx files with NPOI - Excel cannot open the file 'file.xlsx" because the file format or file extension is not valid

When reading or modifying some user-created .xlsx files, I get the following error message:
We found a problem with some content in 'test.xlsx'. Do you want us to try to recover as much as we can? If you trust the source of this workbook, click Yes.
Clicking Yes gets me another message:
Excel cannot open the file 'test.xlsx' because the file format or file extension is not valid. Verify that the file has not been corrupted and that the file extension matches the format of the file.
Example of a problem .xlsx file here (before put in NPOI).
Here's the same file, now corrupted after being read from and written back with iWorkbook.Write(filestream); here.
I have no issues creating a new .xlsx file with the following code:
string newPath = #"C:\MyPath\test.xlsx";
using (FileStream fs = new FileStream(newPath, FileMode.Create, FileAccess.Write))
{
IWorkbook wb = new XSSFWorkbook();
wb.CreateSheet();
ISheet s = wb.GetSheetAt(0);
IRow r = s.CreateRow(0);
r.CreateCell(0);
ICell c = r.GetCell(0);
c.SetCellValue("test");
wb.Write(fs);
fs.Close();
}
That works fine.
Even opening one of the problem child .xlsx files, setting it to an IWorkbook and writing it back to the file works:
string newPath = #"C:\MyPath\test.xlsx";
using (FileStream fs = new FileStream(newPath, FileMode.Open, FileAccess.ReadWrite))
{
IWorkbook wb = new XSSFWorkbook(fs);
wb.Write(fs);
fs.Close();
}
However, after running through code that reads from it, gets ISheets, IRows, ICells, etc.... it corrupts the .xlsx file. Even though I specifically removed anything that modifies the workbook. No Creates, Sets, Styles, etc. with NPOI.
I can't really include my code because it would just be confusing, but for the sake of completeness I'm really only using the following types and functions from NPOI during this test:
IWorkbook
XSSFWorkbook
ISheet
IRow
ICell
.GetSheetAt
.GetRow
.GetCell
.LastRowNum
So one of those causes corruption. I would like to eventually set values again and get it working like I have for .xls.
Has anyone experienced this? What are some NPOI functions that could cause corruption? Any input would be appreciated.
Edit: Using NPOI v2.2.1.

I think the problem is that you are reading from, and writing to, the same FileStream. You should be doing the read and write using separate streams.
Try it like this:
string newPath = #"C:\MyPath\test.xlsx";
// read the workbook
IWorkbook wb;
using (FileStream fs = new FileStream(newPath, FileMode.Open, FileAccess.Read))
{
wb = new XSSFWorkbook(fs);
}
// make changes
ISheet s = wb.GetSheetAt(0);
IRow r = s.GetRow(0) ?? s.CreateRow(0);
ICell c = r.GetCell(1) ?? r.CreateCell(1);
c.SetCellValue("test2");
// overwrite the workbook using a new stream
using (FileStream fs = new FileStream(newPath, FileMode.Create, FileAccess.Write))
{
wb.Write(fs);
}

I had the same problem. In my case the problem was not with the NPOI itself but with its dependency, SharpZipLib.
I used NPOI 2.3.0 and SharpZipLib 1.0.0. and it was given the the same error as in your case. The generated Excel was 0 bytes in size.
I downgraded the SharpZipLib back to 0.86.0 in the project where I was using the NPOI (a Service layer) and also in the MVC project(I had the package of SharpZipLib here too).
I also removed manually in web.config the assembly dependency previously created for SharpZipLib:
<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
.......
<dependentAssembly>
<assemblyIdentity name="ICSharpCode.SharpZipLib" publicKeyToken="1b03e6acf1164f73" culture="neutral" />
<bindingRedirect oldVersion="0.0.0.0-1.0.0.999" newVersion="1.0.0.999" />
</dependentAssembly>
</assemblyBinding>
I hope this helps someone.

I had the same error attempting to write the excel file to a memory stream and then downloading through my .net Core controller.
This code was my problem (At this point, workbook contained the NPOI excel file I created):
var fileName = $"export.xlsx";
var mimeType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
MemoryStream stream = new();
workbook.Write(stream);
byte[] output = stream.GetBuffer();
return File(output, mimeType, fileName);
The issue was this line:
byte[] output = stream.GetBuffer();
That line gave me a byte array that contained the contents of my excel file, but I did not realize that the GetBuffer returned not only the byte array representing the excel file, but also the remaining allocated memory for the byte array.
I replaced that line with this:
byte[] output = stream.ToArray();
and life was good.

When writing back to the file, be sure to use Create as FileMode method. If you use Open, the file will be corrupted because it will concatenate the new file at the end of the old one.
IWorkbook workbook;
using (FileStream file = new FileStream(filePath, FileMode.Open, FileAccess.Read))
{
workbook = new XSSFWorkbook(file);
}
// do things to workbook...
using (FileStream file = new FileStream(filePath, FileMode.Create, FileAccess.Write))
{
workbook.Write(file);
}

is it possible to edit .xlsm files using NPOI with C#

Thanks for the help from people on this site, I was able to modify .xlsx file using NPOI. Code is below, but my final goal is to be able to modify .xlsm file cell value. Is there a way to do this? I tried to run with the following code but after won't be able to open the file once i ran the program.
XSSFWorkbook templateWorkbook;
using (FileStream fs = new FileStream(#"C:\Users\jzhu\Desktop\FlexTimeSheetTest.xlsm", FileMode.Open, FileAccess.ReadWrite))
{
templateWorkbook = new XSSFWorkbook(fs);
fs.Close();
}
XSSFSheet sheet = (XSSFSheet)templateWorkbook.GetSheet("Sheet1");
sheet.GetRow(0).GetCell(0).SetCellValue("Drago");
sheet.ForceFormulaRecalculation = true;
File.Delete(#"C:\Users\jzhu\Desktop\FlexTimeSheetTest.xlsm");
using (FileStream file = new FileStream(#"C:\Users\jzhu\Desktop\FlexTimeSheetTest.xlsm", FileMode.CreateNew, FileAccess.Write))
{
templateWorkbook.Write(file);
file.Close();
}

Update your NPOI library to latest version (2.1.3.1 at present time).
Using this version, your code and sample xlsm file with one macro recorded - I got valid file after modifying it by your code.
Excel is able to open it, and macro can be run.

XSSFWorkbook xlWorkbook;
using (FileStream file = new FileStream(toEditFile,FileMode.Open, FileAccess.Read))
{
xlWorkbook = new XSSFWorkbook(file);
}
var xlWorksheet = xlWorkbook.GetSheet(#"sheet");
// do stuff
using (FileStream file = new FileStream(toEditFile, FileMode.Create, FileAccess.Write))
{
xlWorkbook.Write(file);
file.Close();
}

Editing and saving xlsx with NPOI results in a corrupted file

FileStream s = new FileStream(#myPath, FileMode.Open, FileAccess.ReadWrite);
IWorkbook wb = new XSSFWorkbook(s);
s.Close();
ISheet isheet = wb.GetSheetAt(0);
IRow irow = isheet.CreateRow(0);
irow.CreateCell(0).SetCellValue("foo");
s = new FileStream(#myPath + "blah.xlsx", FileMode.Create);
wb.Write(s);
s.Close();
New file is created but corrupted. I've seen people say this is fixed in version 2.0.6, but still not working for me.

Looks like you are using #myPath as the share / file name on line 1 of your code to create a Stream, yet you concatenate a file name onto #myPath to save the file. Could this be the source of the error?