HTTP Post: Issue with posting XML with credentials

I need help/ suggestion/ idea/ or similar with Http Post. I'm having issues with posting XML file to URL with credentials. Server that I need to post have two text boxes for username and password and upload button to choose file for uploading/ posting. My code looks like all examples that I've found online: I'm sending credentials as NameValueCollection, content type as multipart/form-data etc. I'm also getting Acknowledgment that file is posted successfully (same acknowledgement I get when post file manually). But, record in database for posted file is missing when I post using my code. I really don`t know what can be the issue, because same method works just fine with other type of XML (one with namespaces, envelopes etc). This file I want to post does not have namespace, just basic structure like this:

<Test>
  <TestID>someInfo</TestID>
  <Name>someNAme</Name>
</Test> 

Does anyone have idea what can be the issue and how can I solve it? Thank you very much in advance.

Here's code I'm using:

public static void HttpPost(string xmlFile, string url, string username, string password)
    {
        NameValueCollection formData = new NameValueCollection();
        string result = null;
        formData["Username"] = username;
        formData["Password"] = password;

        string boundary = "----------------------------" + DateTime.Now.Ticks.ToString("x");
        System.Net.WebRequest webRequest = System.Net.WebRequest.Create(url);

        var request = (HttpWebRequest)(WebRequest.Create(url));

        request.Method = "POST";
        request.ContentType = "multipart/form-data; boundary=" + boundary;
        request.Credentials = CredentialCache.DefaultCredentials;

        // Ignore Certificate validation failures
        ServicePointManager.ServerCertificateValidationCallback = ((sender, certificate, chain, sslPolicyErrors) => true);

        Encoding encoding = Encoding.UTF8;

        try
        {
            Stream postDataStream = GetPostStream(xmlFile, formData, boundary, encoding);

            byte[] bytes = new byte[postDataStream.Length];
            postDataStream.Position = 0;
            postDataStream.Read(bytes, 0, (int)bytes.Length);

            string data = encoding.GetString(bytes);
            byte[] byteArray = encoding.GetBytes(data);

            webRequest.ContentLength = byteArray.Length;
            request.ContentLength = byteArray.Length;

            ServicePoint point = request.ServicePoint;
            point.ReceiveBufferSize = 2048;
            point.ConnectionLeaseTimeout = Timeout.Infinite;
            request.ServicePoint.Expect100Continue = false;

            Stream dataStream = request.GetRequestStream();
            dataStream.Write(byteArray, 0, byteArray.Length);
            dataStream.Close();
            WebResponse response = request.GetResponse();
            dataStream = response.GetResponseStream();.
            StreamReader reader = new StreamReader(dataStream);
            result = reader.ReadToEnd();
            postDataStream.Close();

        }
        catch (Exception e)
        {
            throw new Exception(String.Format("Failed Stream {0}", e.InnerException));
        }

GetPostStream Method:

 private static Stream GetPostStream(string filepath, NameValueCollection formData, string boundary, Encoding encoding)
    {
        Stream postDataStream = new System.IO.MemoryStream();

        try
        {
            string formDataHeaderTemplate = Environment.NewLine + "--" + boundary + Environment.NewLine +
            "Content-Disposition: form-data; name=\"{0}\";" + Environment.NewLine + Environment.NewLine + "{1}";

            foreach (string key in formData.Keys)
            {
                byte[] formItemBytes = encoding.GetBytes(string.Format(formDataHeaderTemplate,
                key, formData[key]));
                postDataStream.Write(formItemBytes, 0, formItemBytes.Length);
            }
           FileInfo fileInfo = new FileInfo(filepath);

            string fileHeaderTemplate = Environment.NewLine + "--" + boundary + Environment.NewLine +
            "Content-Disposition: form-data; name=\"{0}\"; filename=\"{1}\"" +
            Environment.NewLine + "Content-Type: text/xml" + Environment.NewLine + Environment.NewLine;

            byte[] fileHeaderBytes = encoding.GetBytes(string.Format(fileHeaderTemplate,
            "HTTPPOSTFILE", fileInfo.FullName));

            postDataStream.Write(fileHeaderBytes, 0, fileHeaderBytes.Length);

            FileStream fileStream = fileInfo.OpenRead();

            byte[] buffer = new byte[fileStream.Length];

            int bytesRead = 0;

            while ((bytesRead = fileStream.Read(buffer, 0, buffer.Length)) != 0)
            {
                postDataStream.Write(buffer, 0, bytesRead);
            }

            fileStream.Close();

            byte[] endBoundaryBytes = encoding.GetBytes("--" + boundary + "--");
            postDataStream.Write(endBoundaryBytes, 0, endBoundaryBytes.Length);

        }

        catch (Exception e)
        {

            throw new Exception(e.InnerException.ToString());
        }

        return postDataStream;
    }