Download files with ServiceStack Rest-API

Question

I'm quite new to REST-services in general and I'm playing around with ServiceStack (which is awesome!). I have some services running and now I want to be able to download files (zip) via the service.

My idea is to set a route (/download) to receive files and download them with the client to store them locally.

My current approach looks like this:

[Route("/download")] public class DownloadRequest : IReturn<HttpResult> { } public class FileDownloadService : Service { public object Any(DownloadRequest request) { string fileFullPath = @"C:\Users\marcel\Downloads\test.zip"; string mimeType = "application/zip"; FileInfo fi = new FileInfo(fileFullPath); byte[] reportBytes = File.ReadAllBytes(fi.FullName); HttpResult result = new HttpResult(reportBytes, mimeType); result.Headers.Add("Content-Disposition", "attachment;filename=Download.zip;"); return result; } }

I'd like to change this implementation to send data as stream. I stumbled upon IStreamWriterAsync, but couldn't really find documentation on usage for this. I'd also like to be able to handle client-side download with the ServiceStack C#-Client.

What would be a good strategy do implement my plan?

Edit: Something like that?

[Route("/download")] public class DownloadRequest : IReturn<Stream> { } public class FileDownloadService : Service, IHasOptions { public IDictionary<string, string> Options { get; private set; } public Stream Any(DownloadRequest request) { string fileFullPath = @"C:\Users\marcel\Downloads\test.zip"; FileInfo fi = new FileInfo(fileFullPath); Options = new Dictionary<string, string> { {"Content-Type","application/zip" }, {"Content-Disposition", "attachment;filename=Download.zip;" } }; return fi.OpenRead(); } }

mythz · Accepted Answer · 2017-12-08 10:21:04Z

An easy way to download a file is to return the fileInfo in a HttpResult, e.g:

return new HttpResult(new FileInfo(fileFullPath), asAttachment:true);

Or by using the Virtual File System

return new HttpResult( VirtualFileSources.GetFile(virtualPath), asAttachment:true);

Both of these APIs already write the file bytes as a Stream so there's no need to try manually doing it yourself.

Note: HttpResult is just a server wrapper object not the response body itself so it should never be used in an IReturn<T> interface whose purpose is to tell clients what Response Type the Service returns.

The IReturn<T> should specify what the Response Body is, in this case since it's not a Response DTO it can be either:

IReturn<byte[]> or IReturn<Stream>

Or you can just leave it unspecified as you'll still be able to download it using the ServiceClient's raw data APIs:

With IReturn<Stream> interface:

using (Stream stream = client.Get(new DownloadRequest())) { ... }

Or you can just easily download the response as a Stream without the IReturn<T> by specifying how you want to access the raw data on the call-site, e.g:

Stream stream = client.Get<Stream>(new DownloadRequest()); byte[] bytes = client.Get<byte[]>("/download");

If you want to also access the Response HTTP Headers you can also request the raw HttpWebResponse to be returned which will let you access the Response HTTP Headers:

using (var webRes = client.Get<HttpWebResponse>(new DownloadRequest())) using (var stream = webRes.GetResponseStream()) { var contentDisposition = webRes.Headers[HttpHeaders.ContentDisposition]; }

Alternatively you can also use HTTP Utils to download arbitrary files, e.g:

 string info = null; var bytes = baseUrl.CombineWith("download").GetBytesFromUrl( responseFilter: res => info = res.Headers[HttpHeaders.ContentDisposition]);

Sorry, I don't get it completely yet. When I have a request dto which returns a Stream via IReturn, how can I return an HttpResult with its response dto? To clarify, what must the response dto look like?
Nevermind, I think I got it running! Thanks for your great support!

Tewr · Accepted Answer · 2017-12-12 08:53:12Z

Have a look at this article. Basically, just return a Stream. You can use fi.OpenRead and return that stream.

To combine headers and stream, an option is a custom return type instead, something like this

public class DownloadFileResult : IStreamWriterAsync, IHasOptions { private readonly Stream _stream; public IDictionary<string, string> Options { get; } public DownloadFileResult(Stream responseStream, string mime, string filename) { _stream = responseStream; Options = new Dictionary<string, string>() { {"Content-Disposition", $"attachment; filename=\"{filename}\";"}, {"Content-Type", mime} }; } public async Task WriteToAsync(Stream responseStream, CancellationToken token) { if (_stream == null) { return; } await _stream.CopyToAsync(responseStream); responseStream.Flush(); } }

Thanks! I think I get what you say, but how would I then connect stream, options and service? I've added some code to my question.
Sorry my first answer was not very clear and not very correct either, see edit

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