Post Stream in ASP.NET Core Web Api

Question

Hello lovely people of Stack Overflow. Since yesterday I have a problem and I have been browsing SO since then. I have a UWP Client and ASP.NET Core Web Api. I just want to send a stream to my web api but indeed this occurred to be harder task than i thought.

I have a class which I have only one property. The Stream property as you can see below:

public class UploadData
{
    public Stream InputData { get; set; }
}

Then Here is my code from my Web Api:

// POST api/values
[HttpPost]
public string Post(UploadData data)
{
    return "test";
}

I have tried to read the stream From body but the result is same. I can hit the post method UploadData is not null but my InputData is always null.

Here is my UWP's code for post request.

private async void PostStreamButton_OnClick(object sender, RoutedEventArgs e)
{
    using (var client = new HttpClient())
    {
        var dummyBuffer = new UnicodeEncoding().GetBytes("this is dummy stream");
        var dummyStream = new MemoryStream(dummyBuffer).AsRandomAccessStream().AsStream();

        var requestContent = new MultipartFormDataContent();
        var inputData = new StreamContent(dummyStream);
        inputData.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
        requestContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");

        requestContent.Add(inputData, "inputData");

        HttpResponseMessage response = client.PostAsync("url", inputData).Result;
    }
}

I have tried various of content types which none of them seems to work and I have no idea why. I would really appreciate all the help.

Nkosi · Accepted Answer · 2017-02-16 15:11:52Z

20

On client side send the stream content not the whole model.

private async void PostStreamButton_OnClick(object sender, RoutedEventArgs e) {
    using (var client = new HttpClient()) {
        var dummyBuffer = new UnicodeEncoding().GetBytes("this is dummy stream");
        var dummyStream = new MemoryStream(dummyBuffer).AsRandomAccessStream().AsStream();

        var inputData = new StreamContent(dummyStream);

        var response = await client.PostAsync("url", inputData);
    }
}

NOTE: Do not mix .Result blocking calls with async calls. Those tend to cause deadlocks.

On server update action

// POST api/values
[HttpPost]
public IActionResult Post() {
    var stream = Request.Body;
    return Ok("test");
}

edited Feb 16, 2017 at 15:11

answered Feb 16, 2017 at 14:58

Nkosi

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6 Comments

Hasan Hasanov Over a year ago

Hello, I dont have Content property on my Request. I only have body.

Nkosi Over a year ago

@HasanHasanov, You are correct. My code was for previous version. Body is what you should be looking for.

Jeremy Armstrong Over a year ago

Out of curiosity, how does this work behind the scenes. When you get a StreamContent (or any streamable thing) as an input/output of a service call, does the request/response just stay open until you dispose the stream object? Trying to visualize how this works behind the scenes.

Nkosi Over a year ago

@JeremyArmstrong take a look at the StreamContent class for client side. pay attention to SerializeToStreamAsync method

Nkosi Over a year ago

On the server side it keeps the stream open till it is done with the request. if it closes it before the request/response is complete, not all the data will be sent.

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