class WebAPIRequester
    {
        public WebAPIRequester() { }
        private string requestUrlString;
        private string authorizationString;
        private string contentType;
        private string acceptType;


        public void Connect(string requestUrlString, string authorizationString, string contentType, string acceptType)
        {
            this.requestUrlString = requestUrlString;
            this.authorizationString = authorizationString;
            this.contentType = contentType;
            this.acceptType = acceptType;
        }

        public string GetData(string postData)
        {
            var request = (HttpWebRequest)WebRequest.Create(requestUrlString);

            var data = Encoding.UTF8.GetBytes(postData);

            request.Method = "POST";
            request.PreAuthenticate = true;
            request.Headers.Add("Authorization", this.authorizationString);
            request.ContentType = this.contentType;
            request.Accept = this.acceptType;
            request.ContentLength = data.Length;

            using (var stream = request.GetRequestStream())
            {
                stream.Write(data, 0, data.Length);
            }

            var response = (HttpWebResponse)request.GetResponse();
            var responseString = new StreamReader(response.GetResponseStream()).ReadToEnd();

            return responseString;
        }

        public string GetData<T>(T operation)
        {
            return GetData(FormatPostData(operation));
        }

        private string FormatPostData<T>(T operation)
        {
            var serializer = new XmlSerializer(typeof(T));
            string result;
            using (var sww = new StringWriter())
            {
                using (var writer = XmlWriter.Create(sww))
                {
                    serializer.Serialize(writer, operation, new XmlSerializerNamespaces());
                    result = sww.ToString();
                }
            }
            return result;
        }

    }