求助...我无法弄清楚为什么HttpWebRequest.GetRequestStream()会抛出超时异常...每次使用POST建立第二个（以及后续）连接时，它总是发生。基本上，我正在尝试每30秒创建一次连接。以下是相关代码:
我的主循环：
for( int i = 0; i < students.Count; i++ ) {
Log( "Processing: " + students[i].DbID + ";" + students[i].Username + ";" + students[i].Password );
UserConnection uc = new UserConnection( students[i] );
uc.ParseAll();
Log( "Done Processing: " + students[i].DbID + ";" + students[i].Username + ";" + students[i].Password );
}
来自用户连接：
public UserConnection( Student student )
{
this.student = student;
this.cookies = new CookieContainer();
this.InitCookies();
this.courses = new List<Course>();
}
private void InitCookies()
{
HttpWebRequest req = (HttpWebRequest)WebRequest.Create( baseUri );
req.Method = "GET";
req.CookieContainer = this.cookies;
req.GetResponse();
}
public void ParseAll()
{
ParseCourseInfo(); //get info for each class
.
.
.
}
private void ParseCourseInfo()
{
HtmlDocument page = GetPage( "POST", homeUri, "username=" + student.Username + "&password=" + student.Password + "&testcookies=1" );
.
.
.
}
以下异常在GetPage中发生：
29/07/2012 1:04:22 PM : Exception: System.Net.WebException
Message: The operation has timed out
Source: System
Stack Trace: at System.Net.HttpWebRequest.GetRequestStream(TransportContext& context)
at System.Net.HttpWebRequest.GetRequestStream()
at URCoursesParserV2.UserConnection.GetPage(String method, Uri pageUri, String queryString) in UserConnection.cs:line 167
这里是存在问题的GetPage代码：
private HtmlDocument GetPage( string method, Uri pageUri, String queryString = "" )
{
Stream data = null;
HttpWebResponse res = null;
HttpWebRequest req = null;
try {
req = (HttpWebRequest)WebRequest.Create( pageUri );
req.CookieContainer = this.cookies;
req.Timeout = 1000 * 10; //10 seconds - I've also tried leaving it as default
req.KeepAlive = false; ////I've also tried leaving it as true.
if( method.ToUpper() == "POST" ) {
req.Method = "POST";
if( queryString != "" ) {
byte[] postBytes = Encoding.UTF8.GetBytes( queryString );
req.ContentType = "application/x-www-form-urlencoded";
req.ContentLength = postBytes.Length;
using( data = req.GetRequestStream() ) { //////////////EXCEPTION HERE ON SECOND ITERATION
data.Write( postBytes, 0, postBytes.Length );
data.Close();
}
}
} else if( method.ToUpper() == "GET" ) {
req.Method = "GET";
if( queryString != "" ) {
pageUri = new Uri( pageUri.ToString() + '?' + queryString );
}
} else {
return null;
}
HtmlDocument page = null;
using( res = (HttpWebResponse)req.GetResponse() ) {
using( data = res.GetResponseStream() ) {
page = new HtmlDocument();
page.Load( data );
}
}
return page;
} catch(WebException e) {
URCoursesParser.Log( e );
return null;
} catch( Exception e ) {
URCoursesParser.Log( e );
return null;
} finally { ///data and res probably don't need to be checked here now because of 'using' blocks
if( data != null ) {
data.Close();
data = null;
}
if( res != null ) {
res.Close();
res = null;
}
if( req != null ) {
req.Abort();
req = null;
}
}
}
有什么想法吗？！第一次迭代总是没问题的。如果我终止程序并重新启动，第一次迭代再次没有问题……始终是第二次和后续的迭代出现问题。