I'm connecting to an on-prem 2016 SharePoint system.

I'm trying to use REST to download a file from a doc library. I'm able to create the REST call, however the data I'm being returned looks jumbled...

The call:

using (var client = new WebClient())
    client.Headers.Add(HttpRequestHeader.ContentType, "application/json;odata=verbose");
    client.Headers.Add(HttpRequestHeader.Accept, "application/json;odata=verbose");
    client.Headers.Add(HttpRequestHeader.ContentEncoding, "UTF-8");

    client.Headers.Add(HttpRequestHeader.Cookie, FedAuthToken);
    var endpointUri = new Uri("https://test.mycorp.com/sites/RESTPOC/_api/web/getfilebyserverrelativeurl('/sites/RESTPOC/Shared%20Documents/banner-05.jpg')/OpenBinaryStream");
    var result = client.DownloadString(endpointUri);

The output of 'Result' looks like:

"ÿØÿá\0\u0018Exif\0\0II*\0\b\0\0\0\0\...goes on quite a while...

Any advice on how I should handle this, and the best way to stream this into an actual file?


3 Answers 3


You asked for JSON as your response format, and you got a JavaScript encoded string back. Maybe try:

client.Headers.Add(HttpRequestHeader.Accept, "image/jpeg");


client.Headers.Add(HttpRequestHeader.Accept, "application/octet-stream");
  • Thanks, however the response still looks scrambled, even after trying the different headers. I've also tried encoding it into an array: byte[] byteArray = Encoding.UTF8.GetBytes(result); --> without success. Mar 13, 2018 at 9:08
  • You just dont use DownloadString method... there needs to be method to download byte array, isnt there DownloadData?
    – michalh
    Feb 15, 2019 at 9:04

Found the solution, I should have been using client.DownloadData rather than client.DownloadString.

Also, included the additional header as provided in the first answer:

using (var client = new WebClient())
            client.Headers.Add(HttpRequestHeader.Accept, "application/octet-stream");
            client.Headers.Add("binaryStringRequestBody", "true");

            client.Headers.Add(HttpRequestHeader.Cookie, cook2);
            var endpointUri = new Uri("https://collab.myCorp.com/sites/RESTPOC/_api/web/getfilebyserverrelativeurl('/sites/RESTPOC/Shared%20Documents/banner-05.jpg')/OpenBinaryStream");
            var result = client.DownloadData(endpointUri);

            MemoryStream stream = new MemoryStream(result);
            File.WriteAllBytes("C:\\temp\\image.jpg", result);

  • what is cook2?? Jun 18, 2019 at 12:20
  • Its the FedAuth cookie value Jun 18, 2019 at 16:08

Here is a demo for your reference:

//Create a stream for the file
Stream stream = null;

//This controls how many bytes to read at a time and send to the client
int bytesToRead = 10000;

// Buffer to read bytes in chunk size specified above
byte[] buffer = new Byte[bytesToRead];

// The number of bytes read
  //Create a WebRequest to get the file
  HttpWebRequest fileReq = (HttpWebRequest) HttpWebRequest.Create(url);

  //Create a response for this request
  HttpWebResponse fileResp = (HttpWebResponse) fileReq.GetResponse();

  if (fileReq.ContentLength > 0)
    fileResp.ContentLength = fileReq.ContentLength;

    //Get the Stream returned from the response
    stream = fileResp.GetResponseStream();

    // prepare the response to the client. resp is the client Response
    var resp = HttpContext.Current.Response;

    //Indicate the type of data being sent
    resp.ContentType = "application/octet-stream";

    //Name the file 
    resp.AddHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
    resp.AddHeader("Content-Length", fileResp.ContentLength.ToString());

    int length;
        // Verify that the client is connected.
        if (resp.IsClientConnected)
            // Read data into the buffer.
            length = stream.Read(buffer, 0, bytesToRead);

            // and write it out to the response's output stream
            resp.OutputStream.Write(buffer, 0, length);

            // Flush the data

            //Clear the buffer
            buffer = new Byte[bytesToRead];
            // cancel the download if client has disconnected
            length = -1;
    } while (length > 0); //Repeat until no data is read
    if (stream != null)
        //Close the input stream

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