Problem in uploading PowerPoint file to ZohoShow using HttpWebRequest and multipart/form-Data multipart/form-data

 public static void Upload(string username, string password, string apiKey, string filePath)
        {
            var ticket = GetTicket(username, password);
            if (string.IsNullOrEmpty(ticket)) return;

            var requestUrl = "http://show.zoho.com/api/private/xml/uploadpresentation?apikey=" + 
                apiKey + "&ticket=" + ticket;

            var request = (HttpWebRequest)WebRequest.Create(requestUrl);
            request.Method = "POST";
            //request.Headers = new WebHeaderCollection();
            //request.Headers.Add("Accept", "image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-excel, application/vnd.ms-powerpoint, application/msword, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, application/x-shockwave-flash, */*"); 
            string boundary = "-----------------------------" + DateTime.Now.Ticks.ToString("x");
            //string boundary = "------" + Guid.NewGuid().ToString().Replace("-", "");
            request.ContentType = "multipart/form-data; boundary=" + boundary;
            request.KeepAlive = true;
            request.Credentials =CredentialCache.DefaultCredentials;


            var postDataStream = new MemoryStream();
            const string newLine = "\r\n";
            var streamWriter = new StreamWriter(postDataStream);
            streamWriter.Write(boundary + newLine);
            streamWriter.Write("Content-Disposition: form-data; name=\"content\"; filename=\"" + (new FileInfo(filePath)).Name + "\"" + newLine);
            streamWriter.Write("Content-Type: application/vnd.ms-powerpoint"+ newLine + newLine);
            streamWriter.Flush();

            var fileContent = (new FileInfo(filePath)).OpenText().ReadToEnd();
            streamWriter.Write(fileContent);
            streamWriter.Write(newLine);
            streamWriter.Write(boundary+newLine);
            streamWriter.Flush();

            streamWriter.Write("Content-Disposition: form-data; name=\"submit\"" + newLine + newLine);
            streamWriter.Write("importpresentation" + newLine);
            streamWriter.Write(boundary+ "--" + newLine);
            streamWriter.Flush();

            request.ContentLength = postDataStream.Length;
            using(var requestStream = request.GetRequestStream())
            {
                postDataStream.WriteTo(requestStream);
            }

            streamWriter.Close();
            postDataStream.Close();
            //var content = new StringBuilder();
            //content.AppendLine(boundary);
            //content.AppendLine("Content-Disposition: form-data; name=\"content\"; filename=\"" + (new FileInfo(filePath)).Name + "\"");
            //content.AppendLine("Content-Type: application/vnd.ms-powerpoint");
            //content.AppendLine("");
            //var fileContent = (new FileInfo(filePath)).OpenText().ReadToEnd();
            //content.AppendLine(fileContent);
            //content.AppendLine(boundary);
            //content.AppendLine("Content-Disposition: form-data; name=\"submit\"");
            //content.AppendLine("");
            //content.AppendLine("importpresentation");
            //content.AppendLine(boundary + "--");
            //Console.WriteLine(content);
            //File.WriteAllText(@"e:\a.txt", content.ToString());
            //byte[] data = ASCIIEncoding.UTF8.GetBytes(content.ToString());
            //request.ContentLength = data.Length;

            //var requestStream = request.GetRequestStream();
            //requestStream.Write(data, 0, data.Length);
            //requestStream.Close();

            var response = request.GetResponse();
            // Get the stream containing content returned by the server.
            var responseStream = response.GetResponseStream();
            // Open the stream using a StreamReader for easy access.
            var reader = new StreamReader(responseStream);
            // Read the content.
            var responseFromServer = reader.ReadToEnd();
            Console.WriteLine(responseFromServer);
            // Display the content.
            ///ViewData["content"] = responseFromServer;
            //Console.WriteLine(responseFromServer);
            // Clean up the streams.
            reader.Close();
            responseStream.Close();
            response.Close();
        }