ASP.NET MVC - Download Excel file from MemoryStream (Corrupt file)

Question

I'm trying to make an Excel file download using the in-build downloading in browsers. Basically the download is working fine, after I've created the Excel file within my controller, but when I'm trying to open this file in Excel, I'm told that the file is corrupted:

Excel cannot open the file 'Report.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.

When forcing the file to open in Excel, the sheet is simply empty. I have no idea why this is.

Code

I'm not showing how I'm creating the Excel file, as that's irrelevant (it worked fine before using memory stream).

var stream = wBook.WriteXLSX(); // Return a MemoryStream (Using DTG.Spreadsheet)

return File(stream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "Report.xlsx");

My guess is that you're returning a stream which is positioned at the end, and you just need to add stream.Position = 0; within WriteXLSX - but as Alexander says, we can't tell without seeing it. — Jon Skeet
– Jon Skeet, Commented Mar 4, 2016 at 7:56

Mikhail Tulubaev · Accepted Answer · 2016-03-04 08:00:39Z

18

You should set current stream position to 0 to successfully export your file.

var stream = wBook.WriteXLSX(); // Return a MemoryStream (Using DTG.Spreadsheet)

stream.Seek(0, SeekOrigin.Begin);

return File(stream, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "Report.xlsx");

answered Mar 4, 2016 at 8:00

Mikhail Tulubaev

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4 Comments

Detilium Over a year ago

This one did it for me. Appreciate the assistance.

Aljohn Yamaro Over a year ago

@Detilium may I know what dll you are using for this line wBook.WriteXLSX()?

Detilium Over a year ago

@AljohnYamaro I'm pretty sure it was this one systemexplorer.net/file-database/file/dtg.spreadsheet-dll. Though it's been over 2 years since this SO

Darth Scitus Over a year ago

Jesus H Christ, this bug haunted me for a week. I dont know how I didnt see this answer until now but it worked for me. Thanks dude.

Detilium · Accepted Answer · 2016-03-04 08:28:59Z

4

I think you should return byte array rather than stream. Try using this approach. (This example uses ClosedXML)

 byte[] xlsInBytes;
 using (MemoryStream ms = new MemoryStream())
 {
      workbook.SaveAs(ms);
      xlsInBytes = ms.ToArray();
 }

 return File(xlsInBytes, "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet", "Report.xlsx");

edited Mar 4, 2016 at 8:28

Detilium

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answered Mar 4, 2016 at 8:00

Anton

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