Upload to Sharepoint using FrontPage RPC

Question

Hi,

I am trying to upload documents with their metadata to sharepoint using the RPC method.
well it is working fine except some type of files like docx, xlsx..
I don't get any errors or exceptions, they are(docx, xlsx.) uploaded to sharepoint correctly but without the associated metadata.

How can i fix this problem?

Below is the code i use to upload with metadata:

 private static bool Upload(string webUrl, string documentName, byte[] bytes, Dictionary<string, object> metaInfo, NetworkCredential netAccess, out string result)
    {
        string putOption = "overwrite,createdir,migrationsemantics";  // see http://msdn2.microsoft.com/en-us/library/ms455325.aspx
        string comment = null;
        bool keepCheckedOut = false;
        string method = "method=put+document%3a12.0.4518.1016&service_name=%2f&document=[document_name={0};meta_info=[{1}]]&put_option={2}&comment={3}&keep_checked_out={4}\n";
        method = String.Format(method, documentName, EncodeMetaInfo(metaInfo), putOption, HttpUtility.UrlEncode(comment), keepCheckedOut.ToString().ToLower());
        List<byte> data = new List<byte>();
        data.AddRange(Encoding.UTF8.GetBytes(method));
        data.AddRange(bytes);

       try
        {
            using (WebClient webClient = new WebClient())
            {
                webClient.Credentials = netAccess;
                webClient.Headers.Add("Content-Type", "application/x-vermeer-urlencoded");
                webClient.Headers.Add("X-Vermeer-Content-Type", "application/x-vermeer-urlencoded");
                result = Encoding.UTF8.GetString(webClient.UploadData(webUrl + "/_vti_bin/_vti_aut/author.dll", "POST", data.ToArray()));
                if (result.IndexOf("\n<p>message=successfully") < 0)
                    throw new Exception(result);
            }
        }
        catch (Exception ex)
        {
            result = ex.Message;
            return false;
        }
        return true;
    }