HttpWebRequest request=null;

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

request.Method = "POST";//GET,PUT等

request.Timeout = xxxx;//单位是毫秒

request.ContentType = "xxxx" ;

webRequest.KeepAlive = false;

webRequest.Proxy = null;

System.Net.ServicePointManager.DefaultConnectionLimit = ;

Stream myRequestStream = request.GetRequestStream();

myRequestStream.Write(byte[] buffer, int offset, int count);//写入请求流的内容

myRequestStream.Close();//HttpWebRequest的RequestStream及时关闭

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

Stream myResponseStream = response.GetResponseStream();

//获取返回值

StreamReader myStreamReader = new StreamReader(myResponseStream, Encoding.GetEncoding("utf-8"));

string retString = myStreamReader.ReadToEnd();

myStreamReader.Close();//及时关闭

myResponseStream.Close();//及时关闭

response.Close();//及时关闭

最后要把HttpWebRequest及时关闭释放

if (request != null)

    {

        request.Abort();

    }