schedule task in asp.net 4.X

in global.asax :

Sub TimerElapsed(o As Object)
    log("TASK RUN VIA TIMER")
End Sub

Sub StartBackgroundTasks()
    Dim Timer As System.Threading.Timer = New System.Threading.Timer(New Threading.TimerCallback(AddressOf TimerElapsed), Nothing, New TimeSpan(0), New TimeSpan(0, 0, 30))
End Sub

Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
    StartBackgroundTasks()     '-> start background tasks 
End Sub