public string GetAPIKey(OperationContext oc)
        {
            // get the request
            var request = oc.RequestContext.RequestMessage;
            // get HTTP request message
            var requestProp = (HttpRequestMessageProperty)request.Properties[HttpRequestMessageProperty.Name];
            // get the actual query string
            NameValueCollection queryParams = HttpUtility.ParseQueryString(requestProp.QueryString);

            // return APIKey if there, NameValueCollection returns null if not present
            return queryParams[APIKEY];
        }

using (WebClient client = new WebClient())
            {
                client.Headers.Add("Content-Type", "application/json");
                client.Headers.Add("APIKey","my_generated_key");
                client.Encoding = Encoding.UTF8;
                Console.WriteLine(client.UploadString("http://my_local_host/my.svc/myCall", "POST", data));
            }