How to Download Data as CSV File in .NET API?
If you have to generate a CSV file and return it from a .NET API endpoint, you have to install the CsvHelper NuGet package, and then add the following section:
[HttpGet]
public async Task<IActionResult> ExportAsCsv()
{
Data[] allData = await _service.GetData();
byte[] result;
using (var memoryStream = new MemoryStream())
{
using (var streamWriter = new StreamWriter(memoryStream))
{
using (var csvWriter = new CsvWriter(streamWriter, CultureInfo.InvariantCulture))
{
csvWriter.WriteRecords(allData);
streamWriter.Flush();
result = memoryStream.ToArray();
}
}
}
return new FileStreamResult(new MemoryStream(result), "text/csv")
{
FileDownloadName = "filename.csv"
};
}
It creates an array of bytes (byte[] result), with the data expected to be part of the CSV file, and then uses it to create a FileStreamResult of type text/csv, whose filename is defined with the property FileDownloadName.