Mvc - How to stream large file in 4k chunks for download

Question

i was following this example, but when download starts it hangs and than after a minute it shows server error. I guess response end before all data id sent to client.

Do you know another way that i can do this or why it's not working?

Writing to Output Stream from Action

private void StreamExport(Stream stream, System.Collections.Generic.IList<byte[]> data)
        {
            using (BufferedStream bs = new BufferedStream(stream, 256 * 1024))
            using (StreamWriter sw = new StreamWriter(bs))
            {
                foreach (var stuff in data)
                {
                    sw.Write(stuff);
                    sw.Flush();
                }

            }
        }

Just noticed your buffer size is 256 * 1024 which is 256kB which is a huge buffer. This is probably the problem but I posted a different approach as an answer. Change your buffer to 4096 and see what happens. Generally more than a 10kB buffer is not good. — ManOVision, May 12 '16 at 14:20

score 1 · Accepted Answer · edited Apr 11 '17 at 18:46

Can you show the calling method? What is the Stream being passed in? Is it the Response Stream?

There are many helpful classes to use that you don't have to chuck yourself because they chunk by default. If you use StreamContent there is a constructor overload where you can specify buffer size. I believe default is 10kB.

From memory here so it my not be complete:

[Route("download")]
[HttpGet]
public async Task<HttpResponseMessage> GetFile()
{
    var response = this.Request.CreateResponse(HttpStatusCode.OK);

    //don't use a using statement around the stream because the framework will dispose StreamContent automatically

    var stream = await SomeMethodToGetFileStreamAsync();

    //buffer size of 4kB
    var content = new StreamContent(stream, 4096);

    response.Content = content;

    return response;
}

Mvc - How to stream large file in 4k chunks for download

1 Answers1