send byte array by HTTP POST in store app

Question

I'm trying to send some images + some meta data to a server by HTTP post from a windows store app but get stuck when trying to actually include the data in the post. It cannot be done the way you would accomplish this in a windows forms app or similar due to the changes to the store app API.

I get the error.

cannot convert source type byte[] to target type System.Net.Http.httpContent

now this is obviously because it's 2 different types that can't be implicitly casted, but it's basically what I'm looking to be able to do. How do I make get my byte array data into the httpContent type so I can include it in the following call

httpClient.PostAsync(Uri uri,HttpContent content);

here's my full upload method:

async private Task UploadPhotos(List<Photo> photoCollection, string recipient, string format)
    {
        PhotoDataGroupDTO photoGroupDTO = PhotoSessionMapper.Map(photoCollection);

        try
        {
            var client = new HttpClient();
            client.MaxResponseContentBufferSize = 256000;
            client.DefaultRequestHeaders.Add("Upload", "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)");

            // POST action_begin
            const string actionBeginUri = "http://localhost:51139/PhotoService.axd?action=Begin";
            HttpResponseMessage response = await client.GetAsync(actionBeginUri);
            response.EnsureSuccessStatusCode();
            string responseBodyAsText = await response.Content.ReadAsStringAsync();
            string id = responseBodyAsText;
            ////

            // POST action_upload
            Uri actionUploadUri = new Uri("http://localhost:51139/PhotoService.axd?action=Upload&brand={0}&id={1}&name={2}.jpg");

            var metaData = new Dictionary<string, string>()
            {
                {"Id", id},
                {"Brand", "M3rror"}, //TODO: Denne tekst skal komme fra en konfigurationsfil.
                {"Format", format},
                {"Recipient", recipient}
            };

            string stringData = "";
            foreach (string key in metaData.Keys)
            {
                string value;
                metaData.TryGetValue(key, out value);
                stringData += key + "=" + value + ",";
            }

            UTF8Encoding encoding = new UTF8Encoding();
            byte[] byteData = encoding.GetBytes(stringData);

            HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, actionUploadUri);

            // send meta data
            // TODO get byte data in as content
            HttpContent metaDataContent = byteData;
            HttpResponseMessage actionUploadResponse = await client.PostAsync(actionUploadUri, metaDataContent);

            actionUploadResponse.EnsureSuccessStatusCode();
            responseBodyAsText = await actionUploadResponse.Content.ReadAsStringAsync();

            // send photos
            // TODO get byte data in as content
            foreach (byte[] imageData in photoGroupDTO.PhotosData)
            {
                HttpContent imageContent = imageData;
                actionUploadResponse = await client.PostAsync(actionUploadUri, imageContent);
                actionUploadResponse.EnsureSuccessStatusCode();
                responseBodyAsText = await actionUploadResponse.Content.ReadAsStringAsync();
            }                
            ////

            // POST action_complete
            const string actionCompleteUri = "http://localhost:51139/PhotoService.axd?action=Complete";
            HttpResponseMessage actionCompleteResponse = await client.GetAsync(actionCompleteUri);
            actionCompleteResponse.EnsureSuccessStatusCode();
            responseBodyAsText = await actionCompleteResponse.Content.ReadAsStringAsync();
            ////
        }

        catch (HttpRequestException e)
        {
        }
        catch (Exception e)
        {
            Debug.WriteLine(e.ToString());
        }
    }

Doesn't the binary data need to be serialised? Also you probably want to stream it rather than upload it all at once. stackoverflow.com/questions/19005991/… may help. — bytefire
– bytefire, Commented May 7, 2014 at 13:21

kiewic · Accepted Answer · 2023-03-10 05:07:57Z

67

It will be more straightforward to use System.Net.Http.ByteArrayContent. E.g:

// Converting byte[] into System.Net.Http.HttpContent.
byte[] data = new byte[] { 1, 2, 3, 4, 5};
ByteArrayContent byteContent = new ByteArrayContent(data);
HttpResponseMessage response = await client.PostAsync(uri, byteContent);

For text only with an specific text encoding use:

// Convert string into System.Net.Http.HttpContent using UTF-8 encoding.
StringContent stringContent = new StringContent(
    "blah blah",
    System.Text.Encoding.UTF8);
HttpResponseMessage response = await client.PostAsync(uri, stringContent);

Or as you mentioned above, for text and images using multipart/form-data:

// Send binary data and string data in a single request.
MultipartFormDataContent multipartContent = new MultipartFormDataContent();
multipartContent.Add(byteContent);
multipartContent.Add(stringContent);
HttpResponseMessage response = await client.PostAsync(uri, multipartContent);

edited Mar 10, 2023 at 5:07

answered May 8, 2014 at 16:51

kiewic

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2 Comments

Ganesh Over a year ago

Which is fast enough, secure to process the data which contains the text and numbers combination (around 1lakh records in a list-json serialized)? ByteArrayContent or StringContent. Please suggest

Tim Newton Over a year ago

I think the variable name above should be "response" not "reponse", I was unable to edit it. Caused me issues for a few minutes when copying / pasting into existing code, might save someone else some time if the code is updated with the correct spelling?

Jon · Accepted Answer · 2014-05-14 01:49:38Z

12

You need to wrap the byte array in an HttpContent type.

If you are using System,Net.Http.HttpClient:

HttpContent metaDataContent = new ByteArrayContent(byteData);

If you are using the preferred Windows.Web.Http.HttpClient:

Stream stream = new MemoryStream(byteData);
HttpContent metaDataContent = new HttpStreamContent(stream.AsInputStream());

edited May 14, 2014 at 1:49

answered May 7, 2014 at 18:51

Jon

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2 Comments

Shimmy Weitzhandler Over a year ago

What should be the server-side action pattern for accepting a ByteArrayContent?

cdup Over a year ago

In my case, I'm processing a file uploaded on the server in order to send it to another server's REST API. The use of ByteArrayContent doesn't work. The REST server just gives a status 200 empty reply. However, if I write the uploaded data to a file on the disk and then use the file for a StreamContent, it works. I wonder why.

Ermir · Accepted Answer · 2014-05-07 13:18:48Z

1

The concept you are looking for is called Serialization. Serialization means preparing your data (which could be heterogeneous and without a predefined strucutre) for storage or transmission. Then, when you need to use the data again, you do the opposite operation, deserialization, and get back the original data structure. The link above shows a few methods on how this could be done in C#.

answered May 7, 2014 at 13:18

Ermir

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1 Comment

Stuart Aitken Over a year ago

Nice hint, thanks. Following one answer elsewhere I was decoding form content using UTF-8. Turns out it was being sent as Base64, so that's what I needed to use.

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