HttpWebRequest使用时发生阻塞的解决办法

HttpWebRequest使用如下：

第一种：使用Using 释放资源

     /// <summary>
        /// Http Get请求返回数据
        /// </summary>
        /// <param name="url">Http请求URL</param>
        /// <returns>返回Http请求的结果</returns>
        public string HttpGetMethod(string url, int timeOut = 10)
        {
            string strResult = null;
            try
            {
                if (string.IsNullOrEmpty(url))
                {
                    return null;
                }
                HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
                request.Timeout = timeOut * 1000;
                using (HttpWebResponse wb = (HttpWebResponse)request.GetResponse())
                {
                    using (Stream stream = wb.GetResponseStream())
                    {
                        using (StreamReader streamReader = new StreamReader(stream, Encoding.UTF8))
                        {
                            strResult = streamReader.ReadToEnd();
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                throw;//LoggerService.Log.Error($"Http Get请求{url}返回数据失败，原因：{ex.ToString()}");
            }
            return strResult;
        }

第二种：使用close 释放资源

        /// <summary>
        /// Http Get请求返回数据
        /// </summary>
        /// <param name="url">Http请求URL</param>
        /// <returns>返回Http请求的结果</returns>
        public string HttpGetMethod2(string url, int timeOut = 10)
        {
            if (string.IsNullOrEmpty(url))
            {
                return null;
            }
            HttpWebRequest request = null;
            HttpWebResponse response = null;
            Stream streamReceive = null;
            StreamReader streamReader = null;
            string strResult = null;
            try
            {
                request = (HttpWebRequest)WebRequest.Create(url);
                request.Timeout = timeOut * 1000;
                ServicePointManager.DefaultConnectionLimit = 200;
                response = (HttpWebResponse)request.GetResponse();
                streamReceive = response.GetResponseStream();
                streamReader = new StreamReader(streamReceive, Encoding.UTF8);
                strResult = streamReader.ReadToEnd();
                streamReader.Close();
                streamReader.Dispose();
                streamReceive.Close();
                streamReceive.Dispose();
                response.Close();
                request.Abort();
            }
            catch (Exception ex)
            {
                throw;//   LoggerService.Log.Error($"Http Get请求{url}返回数据失败，原因：{ex.ToString()}");
            }
            finally
            {
                if (streamReader != null)
                {
                    streamReader.Close();
                    streamReader.Dispose();
                }
                if (streamReceive != null)
                {
                    streamReceive.Close();
                    streamReceive.Dispose();
                }
                if (response != null)
                {
                    response.Close();
                }
                
            }
            return strResult;
        }

HttpWebRequest使用的2种基本写法，各种response，streamReceive ，streamReader 资源都释放了，看似没有什问题，其实只要写个while死循环，每次都去请求，你会发现，运行不了几次就阻塞了，原因很简单就是还有个HttpWebRequest对象没有释放，其实很多时候释放了Stream和Response还远远不够，客户端的Request还是在保持着，无法及时释放占有的资源，而是需要Net的GC.Collect()系统垃圾回收器来回收，因此无法保证资源的及时释放，所以一般很容易阻塞，就会出现上次的请求在处理，导致本次请求发送不出去。HttpWebRequest及时释放就是让HttpWebRequest在不需要的时候及时释放资源，这样可以重复使用而不会阻塞。 

在程序的finally中添加下面这句就ok了。

if (request != null)
  {
     request.Abort();
  }