[转]HttpWebRequest使用注意（发生阻塞的解决办法）

HttpWebRequest myRequest  =   null ;
            HttpWebResponse myResponse  =   null ;
            Stream reqStream  =   null ; 
            Stream resStream  =   null ;

             try
             {
                byte[] data = System.Text.Encoding.Default.GetBytes(param);

                myRequest = (HttpWebRequest)WebRequest.Create(url);
                myRequest.Method = "POST";
                myRequest.KeepAlive = true;
                myRequest.ContentType = "application/octet-stream";
                myRequest.ContentLength = data.Length;
                reqStream = myRequest.GetRequestStream();
                reqStream.Write(data, 0, data.Length);
                reqStream.Close();

                myResponse = (HttpWebResponse)myRequest.GetResponse();
                resStream = myResponse.GetResponseStream();
                data = new byte[512];
                int count = 0;
                UIFactory.zZRK_MODIForm.memStream = new MemoryStream();
                while ((count = resStream.Read(data, 0, data.Length)) > 0)
                {
                    UIFactory.zZRK_MODIForm.memStream.Write(data, 0, count);
                }
                resStream.Close();
                
            }
             catch
             {
            }
             finally
             {
                if (resStream != null)
                {
                    resStream.Close();
                }
                if (reqStream != null)
                {
                    reqStream.Close();
                }
                if (myResponse != null)
                {
                    myResponse.Close();
                }
            }

大家看下这段程序，有问题吗？乍一看，好像没有什么问题，所有的流都释放了，Response也释放了。。不过如果你写个循环无限次发起请求，你会发现，运行不了几次就阻塞了。为什么呢？大家看下面的代码

HttpWebRequest myRequest  =   null ;
            HttpWebResponse myResponse  =   null ;
            Stream reqStream  =   null ; 
            Stream resStream  =   null ;

             try
             {
                byte[] data = System.Text.Encoding.Default.GetBytes(param);

                //想服务器端发送请求，获取照片信息
                myRequest = (HttpWebRequest)WebRequest.Create(url);
                myRequest.Method = "POST";
                myRequest.KeepAlive = true;
                myRequest.ContentType = "application/octet-stream";
                myRequest.ContentLength = data.Length;
                reqStream = myRequest.GetRequestStream();
                reqStream.Write(data, 0, data.Length);
                reqStream.Close();

                myResponse = (HttpWebResponse)myRequest.GetResponse();
                resStream = myResponse.GetResponseStream();
                data = new byte[512];
                int count = 0;
                UIFactory.zZRK_MODIForm.memStream = new MemoryStream();
                while ((count = resStream.Read(data, 0, data.Length)) > 0)
                {
                    UIFactory.zZRK_MODIForm.memStream.Write(data, 0, count);
                }
                resStream.Close();
                
            }
             catch
             {
            }
             finally
             {
                if (resStream != null)
                {
                    resStream.Close();
                }
                if (reqStream != null)
                {
                    reqStream.Close();
                }
                if (myResponse != null)
                {
                    myResponse.Close();
                }
                if (myRequest != null)
                {
                    myRequest.Abort();
                }
            }

多了些什么？多了这个

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

其实很多时候释放了Stream和Response还不够，客户端的Request还是在保持着，需要等垃圾回收器来回收，所以一般很容易阻塞，导致请求发送不出去。加上这个就是让HttpWebRequest实例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。 

 

感谢：

http://www.blogjava.net/TiGERTiAN/archive/2010/06/11/227708.html