UnityWebRequest ContentType not Overriding

I am constructing a file post to a REST api. The REST api is specifically looking for mulipart/form-data content. Seems like now matter how I try and override it, the content-type when it gets to the server is always “application/x-www-form-urlencoded”. Does anyone know how to send content as “multipart/form-data”?

byte[] data = File.ReadAllBytes (@"<file location>");

		List<IMultipartFormSection> postForm = new List<IMultipartFormSection> ();

		postForm.Add (new MultipartFormDataSection ("SectionHeader", "data", "text/plain"));
		postForm.Add (new MultipartFormDataSection ("SectionHeader", "data", "text/plain"));
		postForm.Add (new MultipartFormDataSection ("SectionHeader", "data", "text/plain"));
		postForm.Add (new MultipartFormDataSection ("SectionHeader", "data", "text/plain"));
		postForm.Add (new MultipartFormDataSection ("SectionHeader", "data", "text/plain"));
		postForm.Add (new MultipartFormDataSection ("SectionHeader", "data", "text/plain"));
		postForm.Add(new MultipartFormFileSection("SectionHeader", data, "data", "application/octet-stream"));

		string boundaryString = "---NextPart_" + Guid.NewGuid ().ToString () + "---";

		byte[] boundary = Encoding.ASCII.GetBytes (boundaryString);

		UnityWebRequest www = UnityWebRequest.Post(baseApiUrl + dataApiUrl, postForm, boundary);
		www.uploadHandler.contentType = "multipart/form-data";
		www.SetRequestHeader ("Authorization", completeToken.token_type + " " + completeToken.access_token);

		yield return www.Send();

		if(www.isError) {
		else if (www.responseCode != 200) {
			<report responsecode and associated server/client error>
                        //This is where I am getting 415 Unsupported Media Type
			Debug.Log("Form upload complete!");

The following code has worked for me to craft an HTTPWebRequest as a multipart/form-data request. Copying for ease of use (source at the bottom), I have also added some comments to make the code as clear as possible.

///<summary>Uploads form fields, and n files to REST endpoint</summary>
///<param name="url">URL to upload data to</param>
///<param name="files">Array containing string paths to files to upload</param>
///<param name="formFIelds">NameValueCollection containing all non-file fields from the form, default is null if no other fields provided</param>
public static string UploadFilesToRemoteUrl(string url, string[] files, NameValueCollection formFields = null)
    string boundary = "----------------------------" + DateTime.Now.Ticks.ToString("x");

    HttpWebRequest request = (HttpWebRequest) WebRequest.Create(url);
    request.ContentType = "multipart/form-data; boundary=" +
    request.Method = "POST";
    request.KeepAlive = true;
    //stream contains request as you build it
    Stream memStream = new System.IO.MemoryStream();
    var boundarybytes = System.Text.Encoding.ASCII.GetBytes("

–" +
boundary + "
var endBoundaryBytes = System.Text.Encoding.ASCII.GetBytes(”
–" +
boundary + “–”);

    //this is a multipart/form-data template for all non-file fields in your form data
    string formdataTemplate = "

–" + boundary +
Content-Disposition: form-data; name="{0}";


    if (formFields != null)
        //utilizing the template, write each field to the request, convert this data to bytes, and store temporarily in memStream
        foreach (string key in formFields.Keys)
            string formitem = string.Format(formdataTemplate, key, formFields[key]);
            byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
            memStream.Write(formitembytes, 0, formitembytes.Length);
      //this is a multipart/form-data template for all fields containing files in your form data
    string headerTemplate =
        "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"

" +
"Content-Type: application/octet-stream

//Using the template write all files in your files input array to the request
//“uplTheFile” is the destination file’s name
for (int i = 0; i < files.Length; i++)
memStream.Write(boundarybytes, 0, boundarybytes.Length);
var header = string.Format(headerTemplate, “uplTheFile”, files*);*
var headerbytes = System.Text.Encoding.UTF8.GetBytes(header);

memStream.Write(headerbytes, 0, headerbytes.Length);
//Convert files to byte arrays for upload
using (var fileStream = new FileStream(files*, FileMode.Open, FileAccess.Read))*
var buffer = new byte[1024];
var bytesRead = 0;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
memStream.Write(buffer, 0, bytesRead);

memStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);
request.ContentLength = memStream.Length;
//Write the data through to the request
using (Stream requestStream = request.GetRequestStream())
memStream.Position = 0;
byte[] tempBuffer = new byte[memStream.Length];
memStream.Read(tempBuffer, 0, tempBuffer.Length);
requestStream.Write(tempBuffer, 0, tempBuffer.Length);
//Capture the response from the server
using (var response = request.GetResponse())
Stream stream2 = response.GetResponseStream();
StreamReader reader2 = new StreamReader(stream2);
return reader2.ReadToEnd();
Source [StackOverflow][1]
_*[1]: http://stackoverflow.com/a/567460*_

I ran into a similar problem. I think you need to change:

www.uploadHandler.contentType = “multipart/form-data”;


www.SetRequestHeader(“Content-Type”, “multipart/form-data”);