求助在线人数问题！请高手指点．．．

[xt38kma7]

protected void Application_Start(Object sender, EventArgs e)
{

Application["conn"]=ConfigurationSettings.AppSettings["DSN"];
Application["user_sessions"] = 0;
Application["counter_num"]=0;


uint count=0;
StreamReader srd;
//取得文件的实际路径
string file_path=Server.MapPath ("counter.txt");
//打开文件进行读取
srd=File.OpenText (file_path);
while(srd.Peek ()!=-1)
{
string str=srd.ReadLine ();
count=UInt32.Parse (str);
}
object obj=count; //
Application["counter"]=obj;
srd.Close ();




}

protected void Session_Start(Object sender, EventArgs e)
{
Application.Lock();
Application["user_sessions"] = (int)Application["user_sessions"] + 1;
Application.UnLock();

Application.Lock ();
//数值累加，注意这里使用了装箱（boxing）
uint jishu=0;
jishu=(uint)Application["counter"];
jishu=jishu+1;
object obj=jishu;
Application["counter"]=obj;
//将数据记录写入文件
string file_path=Server.MapPath ("counter.txt");
StreamWriter fs=new StreamWriter(file_path,false);
Session.Timeout=1;
fs.WriteLine (jishu);
fs.Close ();
Application.UnLock ();


}

protected void Application_BeginRequest(Object sender, EventArgs e)
{
// Application.Lock();
// Application["counter_num"]=(int)Application["counter_num"]+1;
// Application.UnLock();


}

protected void Application_EndRequest(Object sender, EventArgs e)
{

}

protected void Application_AuthenticateRequest(Object sender, EventArgs e)
{

}

protected void Application_Error(Object sender, EventArgs e)
{

}

protected void Session_End(Object sender, EventArgs e)
{
Application.Lock();
Application["user_sessions"] = (int)Application["user_sessions"] - 1;
Application.UnLock();

}

protected void Application_End(Object sender, EventArgs e)
{
Application.Lock();
Application["user_sessions"] = (int)Application["user_sessions"] - 1;
Application.UnLock();

}
可发现关闭ＩＥ后再次登录人数不是”1”，而是”2”,关闭ＩＥ后再登录又变成了”3”，也就是说”Session_End＂或Application_End没有起作用？这个什么原因？
请高手指点！

[九章落地]

关闭浏览器后，Session并不是马山失效，而是有一个失效时间(timeout，默认是20分钟)，可在web.config里设置。如：
<sessionState mode="InProc" stateConnectionString="tcpip=127.0.0.1:42424" sqlConnectionString="data source=127.0.0.1;Trusted_Connection=yes" cookieless="false" timeout="5"/>