How to return a file using Web API?

Better to return HttpResponseMessage with StreamContent inside of it.

Here is example:

public HttpResponseMessage GetFile(string id)
{
if (String.IsNullOrEmpty(id))
return Request.CreateResponse(HttpStatusCode.BadRequest);


string fileName;
string localFilePath;
int fileSize;


localFilePath = getFileFromID(id, out fileName, out fileSize);
       

HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.OK);
response.Content = new StreamContent(new FileStream(localFilePath, FileMode.Open, FileAccess.Read));
response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
response.Content.Headers.ContentDisposition.FileName = fileName;
response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");


return response;
}

UPDATE from comment by patridge: Should anyone else get here looking to send out a response from a byte array instead of an actual file, you're going to want to use new ByteArrayContent(someData) instead of StreamContent (see here).

I made the follow action:

[HttpGet]
[Route("api/DownloadPdfFile/{id}")]
public HttpResponseMessage DownloadPdfFile(long id)
{
HttpResponseMessage result = null;
try
{
SQL.File file = db.Files.Where(b => b.ID == id).SingleOrDefault();


if (file == null)
{
result = Request.CreateResponse(HttpStatusCode.Gone);
}
else
{
// sendo file to client
byte[] bytes = Convert.FromBase64String(file.pdfBase64);




result = Request.CreateResponse(HttpStatusCode.OK);
result.Content = new ByteArrayContent(bytes);
result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
result.Content.Headers.ContentDisposition.FileName = file.name + ".pdf";
}


return result;
}
catch (Exception ex)
{
return Request.CreateResponse(HttpStatusCode.Gone);
}
}

Example with IHttpActionResult in ApiController.

[HttpGet]
[Route("file/{id}/")]
public IHttpActionResult GetFileForCustomer(int id)
{
if (id == 0)
return BadRequest();


var file = GetFile(id);


IHttpActionResult response;
HttpResponseMessage responseMsg = new HttpResponseMessage(HttpStatusCode.OK);
responseMsg.Content = new ByteArrayContent(file.SomeData);
responseMsg.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
responseMsg.Content.Headers.ContentDisposition.FileName = file.FileName;
responseMsg.Content.Headers.ContentType = new MediaTypeHeaderValue("application/pdf");
response = ResponseMessage(responseMsg);
return response;
}

If you don't want to download the PDF and use a browsers built in PDF viewer instead remove the following two lines:

responseMsg.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
responseMsg.Content.Headers.ContentDisposition.FileName = file.FileName;

Just a note for .Net Core: We can use the FileContentResult and set the contentType to application/octet-stream if we want to send the raw bytes. Example:

[HttpGet("{id}")]
public IActionResult GetDocumentBytes(int id)
{
byte[] byteArray = GetDocumentByteArray(id);
return new FileContentResult(byteArray, "application/octet-stream");
}

I've been wondering if there was a simple way to download a file in a more ... "generic" way. I came up with this.

It's a simple ActionResult that will allow you to download a file from a controller call that returns an IHttpActionResult. The file is stored in the byte[] Content. You can turn it into a stream if needs be.

I used this to return files stored in a database's varbinary column.

    public class FileHttpActionResult : IHttpActionResult
{
public HttpRequestMessage Request { get; set; }


public string FileName { get; set; }
public string MediaType { get; set; }
public HttpStatusCode StatusCode { get; set; }


public byte[] Content { get; set; }


public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
HttpResponseMessage response = new HttpResponseMessage(StatusCode);


response.StatusCode = StatusCode;
response.Content = new StreamContent(new MemoryStream(Content));
response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
response.Content.Headers.ContentDisposition.FileName = FileName;
response.Content.Headers.ContentType = new MediaTypeHeaderValue(MediaType);


return Task.FromResult(response);
}
}

Another way to download file is to write the stream content to the response's body directly:

[HttpGet("pdfstream/{id}")]
public async Task  GetFile(long id)
{
var stream = GetStream(id);
Response.StatusCode = (int)HttpStatusCode.OK;
Response.Headers.Add( HeaderNames.ContentDisposition, $"attachment; filename=\"{Guid.NewGuid()}.pdf\"" );
Response.Headers.Add( HeaderNames.ContentType, "application/pdf"  );
await stream.CopyToAsync(Response.Body);
await Response.Body.FlushAsync();
}

You Can try , HttpClient for Download file from another side and same time you can pass as File Result

 [HttpGet]
[Route("api/getFile")]
public async  Task<FileResult> GetFile(string Param1,string Param2)
{
try
{
Stream stream = null;
string strURL = @"File URL";
HttpClient client = new HttpClient();
HttpResponseMessage httpResponse = await client.GetAsync(strURL);
Stream streamToReadFrom = await httpResponse.Content.ReadAsStreamAsync();
return File(streamToReadFrom, "{MIME TYPE}");


}
catch (Exception ex)
{


throw ex;
}
finally
{
        

}
}