HttpWebRequest使用注意（發生阻塞的解決辦法）

           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();
                }
            }

大家看下這段程式，有問題嗎？乍一看，好像沒有什麼問題，所有的流都釋放了，Response也釋放了。。不過如果你寫個迴圈無限次發起請求，你會發現，執行不了幾次就阻塞了。為什麼呢？大家看下面的程式碼 

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

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

                //想伺服器端傳送請求，獲取照片資訊
                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();
                }
            }

多了些什麼？多了這個

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

其實很多時候釋放了Stream和Response還不夠，客戶端的Request還是在保持著，需要等垃圾回收器來回收，所以一般很容易阻塞，導致請求傳送不出去。加上這個就是讓HttpWebRequest例項在不需要的時候及時釋放資源。這樣可以重複使用而不會阻塞。