public class ApiHelper

    {
　　　　 //contentType application/json or application/xml

        public string HttpGet(string Url, string contentType)

        {

            try

            {

                string retString = string.Empty;

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);

                request.Method = "GET";

                request.ContentType = contentType;

                HttpWebResponse response = (HttpWebResponse)request.GetResponse();

                Stream myResponseStream = response.GetResponseStream();

                StreamReader streamReader = new StreamReader(myResponseStream);

                retString = streamReader.ReadToEnd();

                streamReader.Close();

                myResponseStream.Close();

                return retString;

            }

            catch (Exception ex)

            {

                throw ex;

            }

        }

        public static string HttpPost(string Url, string postDataStr, string contentType, out bool isOK)

        {

            string retString = string.Empty;

            try

            {

                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(Url);

                request.Method = "POST";

                request.ContentType = contentType;

                request.Timeout = ;//设置超时时间

                request.ContentLength = Encoding.UTF8.GetByteCount(postDataStr);

                Stream requestStream = request.GetRequestStream();

                StreamWriter streamWriter = new StreamWriter(requestStream);

                streamWriter.Write(postDataStr);

                streamWriter.Close();

                HttpWebResponse response = (HttpWebResponse)request.GetResponse();

                Stream responseStream = response.GetResponseStream();

                StreamReader streamReader = new StreamReader(responseStream);

                retString = streamReader.ReadToEnd();

                streamReader.Close();

                responseStream.Close();

                isOK = true;

            }

            catch (Exception ex)

            {

                if (ex.GetType() == typeof(WebException))//捕获400错误

                {

                    var response = ((WebException)ex).Response;

                    Stream responseStream = response.GetResponseStream();

                    StreamReader streamReader = new StreamReader(responseStream);

                    retString = streamReader.ReadToEnd();

                    streamReader.Close();

                    responseStream.Close();

                }

                else

                {

                    retString = ex.ToString();

                }

                isOK = false;

            }

            return retString;

        }

    }