该触发条件有2种:
protected virtual Task OnDmtpClosing(
	ClosingEventArgs e
)Protected Overridable Function OnDmtpClosing ( 
	e As ClosingEventArgs
) As Taskabstract OnDmtpClosing : 
        e : ClosingEventArgs -> Task 
override OnDmtpClosing : 
        e : ClosingEventArgs -> Task [缺少 "M:TouchSocket.Dmtp.NamedPipeDmtpSessionClient.OnDmtpClosing(TouchSocket.Sockets.ClosingEventArgs)" 的 <returns> 文档]