HttpWebRequest GET 方式發送數據

/// <summary>
        /// 發送http請求
        /// </summary>
        /// <param name="paras">請求參數</param>
        /// <returns>正常返回接口報文的xml字符串，否則返回空串</returns>
        private string SendHttpRequest(string paras)
        {
            string url ="http://IP:Port/相對路徑"+ "?" + paras;
            HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
            request.Method = "GET";
            request.ContentType = "application/x-www-form-urlencoded";
            request.KeepAlive = false;

            string returnValue = "";
            try
            {
                HttpWebResponse response = request.GetResponse() as HttpWebResponse;
                System.IO.Stream responseStream = response.GetResponseStream();
                System.IO.StreamReader reader = new System.IO.StreamReader(responseStream, Encoding.GetEncoding("GB2312"));
                returnValue = reader.ReadToEnd();
            }
            catch
            {
            }
            return returnValue;
        }