How to send data in csv format from web api controller to react client side for creating visualisations

Question

I have the following code to convert the EF output to CSV file (and save it to the server side and then return it):

   List<LearningActionMonitoringDTO> results = _context
       .LearningActionProgressUpdates
       .Include(la => la.LearningAction)
       .Where(la => la.LearningActionId == actionId)
       .Select(la => new LearningActionMonitoringDTO
       {
           Title = la.LearningAction.Title,
           Progress = la.Progress,
           ProgressDate = la.DateCreated.ToString("g"),

       }).ToList();

   using (var csv = new CsvWriter(new StreamWriter("CSVfiles/Actors.csv")))
   {
       csv.WriteRecords(results);
   }

   FileInfo f = new FileInfo("CSVfiles/Actors.csv");
   return f;

I wonder if I could return the results in CSV format without first saving it to the server. I need the data in CSV file to feed into a React component for creating some charts. Any help?

Sure, you can just return it verbatim, and set the content-type of the response to text/csv. — Moo-Juice
– Moo-Juice, Commented Jul 21, 2019 at 10:52

Moo-Juice · Accepted Answer · 2019-07-21 11:02:44Z

1

Based on my comment, and some code from the author of CsvWriter (assuming it's the same CSV library), to write it to a string, you do the following:

using( var stream = new MemoryStream() )
using( var reader = new StreamReader( stream ) )
using( var writer = new StreamWriter( stream ) )
using( var csv = new CsvWriter( writer ) )
{
    csv.WriteRecords( results);
    writer.Flush();
    stream.Position = 0;
    var text = reader.ReadToEnd();
}

(From here)

Now that you have your CSV file as a chunk of text, we can return it from a Controller thusly:

public ActionResult DownloadCSV()
{
    return Content(yourCsvString, "text/csv");
}

edited Jul 21, 2019 at 11:02

answered Jul 21, 2019 at 10:56

Moo-Juice

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3 Comments

renakre Over a year ago

I have a question. I wonder if I could send the resulting csv as string? The thing is I want to return an object, inside this object I want to include the CSV string as well as other information. I tried ExecuteResult but could not get it work. Any help?

Moo-Juice Over a year ago

@renakre Can you ask that as a separate question, including any supporting details - that way the wider-community will see it :)

renakre Over a year ago

Thanks! Actually I did :) stackoverflow.com/questions/57144160/…

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