asp.net中显示在线用户

private static System.Threading.Timer timer;
private const int interval = 1000 * 60 * 20;//检查在线用户的间隔时间

/// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.IContainer components = null;
public Global()
{
InitializeComponent();
}

protected void Application_Start(Object sender, EventArgs e)
{
if (timer == null)
timer = new System.Threading.Timer(new System.Threading.TimerCallback(ScheduledWorkCallback),
sender, 0, interval);
DataTable userTable = new DataTable();
userTable.Columns.Add("UserID");//用户ID
userTable.Columns.Add("UserName");//用户姓名
userTable.Columns.Add("FirstRequestTime");//第一次请求的时间
userTable.Columns.Add("LastRequestTime");//最后一次请求的时间
userTable.Columns.Add("ClientIP");//
userTable.Columns.Add("ClientName");//
userTable.Columns.Add("ClientAgent");//

userTable.PrimaryKey = new DataColumn[]{userTable.Columns[0]};
userTable.AcceptChanges();
Application.Lock();
Application["UserOnLine"] = userTable;
Application.UnLock();
}

protected void Session_Start(Object sender, EventArgs e)
{
}
protected void Application_BeginRequest(Object sender, EventArgs e)
{

}
protected void Application_EndRequest(Object sender, EventArgs e)
{
}
protected void Application_AcquireRequestState(Object sender, EventArgs e)
{
if(sender == null) return;
if(!(sender is HttpApplication)) return;
HttpApplication mApp = (HttpApplication)sender;
if(mApp.Context.Session == null) return;
if(mApp.Context.Session["UserID"]==null ) return;
string userID = mApp.Context.Session["UserID"].ToString();

if(Application["UserOnLine"] == null) return;
if(!(Application["UserOnLine"] is DataTable)) return;

DataTable userTable = (DataTable)Application["UserOnLine"];
DataRow curRow = userTable.Rows.Find(new object[]{userID});
if(curRow != null)
{
this.GetDataRowFromHttpApp(mApp,ref curRow);
}
else
{
DataRow newRow = userTable.NewRow();
this.GetDataRowFromHttpApp(mApp,ref newRow);
userTable.Rows.Add(newRow);
}
if(userTable.GetChanges()!=null)
{
userTable.AcceptChanges();
Application.Lock();
Application["UserOnLine"] = userTable;
Application.UnLock();
}
}

protected void Application_AuthenticateRequest(Object sender, EventArgs e)
{

}
protected void Application_Error(Object sender, EventArgs e)
{

}

protected void Session_End(Object sender, EventArgs e)
{

}
protected void Application_End(Object sender, EventArgs e)
{

}

#region Web 窗体设计器生成的代码
/// <summary>
/// 设计器支持所需的方法 - 不要使用代码编辑器修改
/// 此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.components = new System.ComponentModel.Container();
}
#endregion
private void GetDataRowFromHttpApp(HttpApplication mApp,ref DataRow mRow)
{
if(mApp.Context.Session == null) return;
if(mApp.Context.Session["UserID"]==null || mApp.Context.Session["UserName"]==null) return;
string userID = mApp.Context.Session["UserID"].ToString();
string userName = mApp.Context.Session["UserName"].ToString();
if(mRow.RowState == DataRowState.Detached)
{
mRow["UserID"] = userID;
mRow["UserName"] = userName;
mRow["FirstRequestTime"] = System.DateTime.Now;
mRow["ClientIP"] = mApp.Context.Request.UserHostAddress;
mRow["ClientName"] = mApp.Context.Request.UserHostName;
mRow["ClientAgent"] = mApp.Context.Request.UserAgent;
mRow["LastRequestTime"] = System.DateTime.Now;
}
else if(!mRow.IsNull("LastRequestTime"))
{
DateTime time = Convert.ToDateTime(mRow["LastRequestTime"] );
if(((TimeSpan)(DateTime.Now - time)).TotalMinutes>1)
mRow["LastRequestTime"] = System.DateTime.Now;
}
}
private void ScheduledWorkCallback (object sender)
{
string filter = "Convert(LastRequestTime,'System.DateTime') < Convert('" + System.DateTime.Now.AddSeconds(-interval/1000).ToString() + "','System.DateTime')";
if(Application["UserOnLine"] == null)
return;
DataTable userTable = (DataTable)Application["UserOnLine"];
DataRow[] lineOutUsers = userTable.Select(filter);
for(int i=0;i<lineOutUsers.Length;i++)
{
DataRow curRow = lineOutUsers[i];

//保存到数据库...
}
if(userTable.GetChanges()!=null)
{
userTable.AcceptChanges();
Application.Lock();
Application["UserOnLine"] = userTable;
Application.UnLock();
}
}
}