When uploading memory stream with contents created by csvhelper using SSH.NET to SFTP server, the uploaded file is empty

Question

I'm truing to send a CSV with csvhelper. But when I send it, it is always empty.

using (var sftProvider =new SFTProvider(Configuration))
using (var csvProvider=new CSVProvider(Configuration))
using (Stream fileStream = new MemoryStream())
{
    var sftp = sftProvider.SFTPConnection("", "", "");
    var nameFile = "/ethias/"+DateTime.Now.ToString(DateFormatConstants.DATE_FORMAT) + ".csv";
    if (sftp.Exists(nameFile))
    {
        sftProvider.ReadFileSFTP(sftp, nameFile, fileStream);
    } 
    await csvProvider.WriteCsv(new List<EthiasResultDTO>() {ethiasResultDto},fileStream); 
    sftProvider.UploadFileSFTP(sftp,nameFile,fileStream);
}

The code for the csv:

public async Task WriteCsv<T>(List<T> csvInfo, Stream stream)
{
    using(var writer = new StreamWriter(stream, Encoding.UTF8))
    using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
    {
        csv.Configuration.Delimiter = ";";

        if ( stream.Length > 0)
        {
            csv.Configuration.HasHeaderRecord = false;
        }
        csv.WriteRecords(csvInfo);
    }
}

i try serveral things but it always empty file that is create .

Into the same fileStream, you first apply ReadFileSFTP(), then WriteCsv() . I think what you do is to get a file from an FTP location, append some records to it, then to put it back. If this is the case, just set fileStream.Position = 0;before passing it to UploadFileSFTP — Oguz Ozgul
– Oguz Ozgul, Commented Mar 15, 2020 at 10:23
If the suggestion by @OguzOzgul does not help, we will need minimal reproducible example. You haven't told us anything about the FTP/SFTP library. It's not even clear if you use FTP or SFTP. — Martin Prikryl
– Martin Prikryl, Commented Mar 15, 2020 at 10:26
i only do the recovery of the record if there a file but i have the problem also when i only create and ad a new file the record in the csv is empty — 20 ans IPl
– 20 ans IPl, Commented Mar 15, 2020 at 11:24

Martin Prikryl · Accepted Answer · 2020-03-15 15:10:14Z

0

You have to seek the read pointer of the stream back to beginning after writing to it. This is covered for example in these questions:
Upload data from memory to SFTP server using SSH.NET
Upload from ByteArray/MemoryStream using SSH.NET - File gets created with size 0KB

For that you also have to make sure that the StreamWriter does not close the memory stream:
Is there any way to close a StreamWriter without closing its BaseStream?

using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
using (var csv = new CsvWriter(writer, CultureInfo.InvariantCulture))
{
    // Write
}

stream.Position = 0;

answered Mar 15, 2020 at 15:10

Martin Prikryl

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