Streaming Json data from an ASP.NET ApiController

Question

I am trying to write an ApiController that streams JSON data in the response. It goes something like this;

public class MyController : ApiController
{
    IDocumentWriter _writer;

    public MyController(IDocumentWriter writer)
    {
        _writer = writer;
    }

    [HttpGet]
    public async Task<HttpResponseMessage> Get()
    {
        var response = Request.CreateResponse(HttpStatusCode.OK);

        using (var stream = new MemoryStream())
        {
            response.Content = new StreamContent(stream);
            await _writer.WriteAsync(stream);
            response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
            response.Content.Headers.ContentLength = stream.Length;
        }

        return response;
    }
}

The IDocumentWriter accepts a stream and writes the JSON data to it. A call to Get fails with a System.Threading.Tasks.TaskCanceledException, which I don't understand because I am awaiting the WriteAsync. Surely it finishes writing before returning? What am I doing wrong?

Answer 1

I figured it out thanks to this post. Turns out I was over complicating things. Here is the final solution;

[HttpGet]
public async Task<HttpResponseMessage> Get()
{
    var response = Request.CreateResponse(HttpStatusCode.OK);

    response.Content = new PushStreamContent(async (stream, content, context) =>
    {
        await _writer.WriteAsync(stream);
        stream.Close();
    }, "application/json");

    return response;
}