public MultipartMimeSendFactory(HttpAsyncRequestFilter filter, XmlDocument xmlRequest, string filename, string encoding, MultipartMimeRequestHelper multipartMimeRequestHelper)
            {
                if (xmlRequest == null)
                {
                    throw new ArgumentNullException();
                }

                // Add boundary to params
                _filename = filename;
                _xmlDoc   = xmlRequest;
                _filter   = filter;
                _multipartMimeRequestHelper = multipartMimeRequestHelper;

                //select the encoding
                _encoding = new UTF8Encoding(false, false);
                try
                {
                    _encoding = Encoding.GetEncoding(encoding);
                }
                catch (Exception ex)
                {
                    //Debug.Fail("Error while getting transport encoding: " + ex.ToString());
                }
            }
            public MultipartMimeSendFactory(HttpRequestFilter filter, XmlDocument xmlRequest, string filename, string encoding, MultipartMimeRequestHelper multipartMimeRequestHelper)
            {
                if (xmlRequest == null)
                    throw new ArgumentNullException();

                // Add boundary to params
                _filename = filename;
                _xmlDoc = xmlRequest;
                _filter = filter;
                _multipartMimeRequestHelper = multipartMimeRequestHelper;

                //select the encoding
                _encoding = new UTF8Encoding(false, false);
                try
                {
                    _encoding = StringHelper.GetEncoding(encoding, _encoding);
                }
                catch (Exception ex)
                {
                    Trace.Fail("Error while getting transport encoding: " + ex.ToString());
                }
            }