C# 操作超时解决办法

net(客户端)调用IIS(服务端)出现503后，就报操作超时错误
问题描述：
服务端环境：
IIS
客户端环境：
windowsxp + iis + .net
调用时出现如下错误:
System.Net.WebException: 远程服务器返回错误: (503) 服务器不可用。
   在 System.Net.HttpWebRequest.GetResponse()
   在 TestWebRequest.WebMessage.SendRequest(Byte[] data, String urlStr)
接着就出现如下错误：
System.Net.WebException: 操作超时
   在 System.Net.HttpWebRequest.GetRequestStream()
最后一直是这个错误
System.Net.WebException: 操作超时
   在 System.Net.HttpWebRequest.GetRequestStream()

 当服务器恢复正常时，访问已经是200时，这个线程还是返回操作超时，经过N多测试，最后如下一行完美解决：

myRequest.ServicePoint.Expect100Continue = false;

修改后：

public byte[] SendRequest(byte[] data, string urlStr)       {           try           {               Stream streamSend = null;               HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(urlStr);               myRequest.Method = "POST";               myRequest.ContentType = "text/xml";               myRequest.Accept = "*/*";               myRequest.Timeout = 2000;               myRequest.UserAgent = "Mozilla-Firefox-Spider(Wenanry)";               myRequest.ContentLength = data.Length;               //这个在Post的时候，一定要加上，如果服务器返回错误，他还会继续再去请求，不会使用之前的错误数据，做返回数据               myRequest.ServicePoint.Expect100Continue = false;               HttpRequestCachePolicy noCachePolicy = new HttpRequestCachePolicy(HttpRequestCacheLevel.NoCacheNoStore);               myRequest.CachePolicy = noCachePolicy;               try               {                   streamSend = myRequest.GetRequestStream();                   streamSend.Write(data, 0, data.Length);                   streamSend.Close();               }               catch (WebException wex)               {                   log.Debug("WebException=" + wex.ToString() + ",wex.Status=" + wex.Status);                   if (streamSend != null)                       streamSend.Close();                   streamSend = null;                   myRequest = null;                   return null;               }               catch (Exception ex)               {                   log.Debug("GetRequestStream=" + ex.ToString());                   if (streamSend != null)                       streamSend.Close();                   myRequest = null;                   return null;               }               byte[] byteArr = new byte[256];               Stream streamRequest = null;               try               {                   streamRequest = myRequest.GetResponse().GetResponseStream();               }               catch (Exception httpex)               {                   log.Debug("SendRequest=" + httpex.ToString());                   if (streamRequest != null)                       streamRequest.Close();                   myRequest = null;                   return null;               }               Bytes bytes = new Bytes();               int count = streamRequest.Read(byteArr, 0, 256);               while (count > 0)               {                   bytes.writeByteArr(Bytes.byteSub(byteArr, 0, count));                   count = streamRequest.Read(byteArr, 0, 256);               }               streamRequest.Close();               return bytes.getByte;           }           catch (Exception eee)           {               log.Debug("eee=" + eee.ToString() + eee.Source + eee.StackTrace);           }           return null;       }