upload files over https - c#-4.0

Question

Can anyone give me a C# code snippet for this kind of file upload:
POST <BASE-URL>/documents
Content-Type: multipart/form-data; boundary=<BOUNDARY>
Transfer-Encoding: chunked
--<BOUNDARY>
Content-Disposition: form-data; name=“metadata”
Content-Type: application/json
{
“metadata” : {
“document” : {
“filename” : <filename>,
“size” : <filesize>,
“title” : <title>,
“author” : <author>
}
}
}
--<BOUNDARY>
Content-Disposition: form-data; name=“document”; filename=“<filename>”
Content-Type: <mime-type>
<File contents>
--<BOUNDARY>--
Currently I am using method shown below and I am getting status 400:Bad Request:
public static void HttpUploadFile(string url, string file, string paramName, string contentType, NameValueCollection nvc,string accessToken)
{
string boundary = "---------------------------" + DateTime.Now.Ticks.ToString("x");
byte[] boundarybytes = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "\r\n");
HttpWebRequest wr = (HttpWebRequest)WebRequest.Create(url);
wr.ContentType = "multipart/form-data; boundary=" + boundary;
wr.Method = "POST";
wr.KeepAlive = false;
wr.SendChunked = true;
wr.Headers.Add("Authorization", "Bearer " + accessToken);
wr.Credentials = System.Net.CredentialCache.DefaultCredentials;
Stream rs = wr.GetRequestStream();
string formdataTemplate = "Content-Disposition: form-data; name=\"{0}\"\r\n\r\n{1}";
foreach (string key in nvc.Keys)
{
rs.Write(boundarybytes, 0, boundarybytes.Length);
string formitem = string.Format(formdataTemplate, key, nvc[key]);
byte[] formitembytes = System.Text.Encoding.UTF8.GetBytes(formitem);
rs.Write(formitembytes, 0, formitembytes.Length);
}
rs.Write(boundarybytes, 0, boundarybytes.Length);
string headerTemplate = "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"\r\nContent-Type: {2}\r\n\r\n";
string header = string.Format(headerTemplate, paramName, file, contentType);
byte[] headerbytes = System.Text.Encoding.UTF8.GetBytes(header);
rs.Write(headerbytes, 0, headerbytes.Length);
FileStream fileStream = new FileStream(file, FileMode.Open, FileAccess.Read);
byte[] buffer = new byte[256000];
int bytesRead = 0;
while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
{
rs.Write(buffer, 0, bytesRead);
}
fileStream.Close();
byte[] trailer = System.Text.Encoding.ASCII.GetBytes("\r\n--" + boundary + "--\r\n");
rs.Write(trailer, 0, trailer.Length);
rs.Close();
WebResponse wresp = null;
try
{
wresp = wr.GetResponse();
Stream stream2 = wresp.GetResponseStream();
StreamReader reader2 = new StreamReader(stream2);
//log.Debug(string.Format("File uploaded, server response is: {0}", reader2.ReadToEnd()));
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
if (wresp != null)
{
wresp.Close();
wresp = null;
}
}
finally
{
wr = null;
}
}
I guess it is the json string part of a post header form-data that gives me the trouble... here it uses namevaluecollection...
Thanx!