How to return a file using Web API?

Question

I am using ASP.NET Web API.
I want to download a PDF with C# from the API (that the API generates).

Can I just have the API return a byte[]? and for the C# application can I just do:

byte[] pdf = client.DownloadData("urlToAPI");?  

and

File.WriteAllBytes()? 

Answer 1

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; } 

UPD 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).

Answer 2

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);     } }