统计网站的在线人数

Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' 在应用程序启动时运行的代码
        Dim dt As DataTable = New DataTable()
        dt.Columns.Add("UIP", GetType(String))
        Dim pk(1) As DataColumn
        pk(0) = dt.Columns("UIP")
        dt.PrimaryKey = pk
        Application("DT") = dt
        dim count as integer=0
        Application("count")=count
 End Sub

 Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
        ' 在新会话启动时运行的代码
        Dim ip As String = Request.ServerVariables("REMOTE_ADDR").ToString  '获取客户端IP地址
        Dim dt As DataTable = Application("DT")
       If dt.Rows.Contains(uid) Then
              Application.Lock()
              Dim Row As DataRow = dt.NewRow()
              Row("UIP") = uid
              dt.Rows.Add(Row)
              Application.Set("DT", dt)
             dim count  as integer=Application("count")
             count+=1
             Application.set("count",count)
             Application.UnLock()
       End If
End Sub

 Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
        Application.Lock()
        Dim ip As String = Request.ServerVariables("REMOTE_ADDR").ToString 
        Try
            Dim i As Integer
            Dim dt As DataTable = Application("DT")
            Dim len as integer=dt.Rows.Count - 1
            For  i = 0  To  len
           Dim row As DataRow = dt.Rows(i)
                If row("UIP").ToString.Equals(ip) Then
                    dt.Rows.Remove(row)
                    Exit For
                End If
            Next
            Application.Set("DT", dt)
             dim count  as integer=Application("count")
             count-=1
             Application.set("count",count)
            Application.UnLock()
        Catch ex As Exception
        End Try
    End Sub
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