diff --git a/NewLife.MQTT/Handlers/IMqttHandler.cs b/NewLife.MQTT/Handlers/IMqttHandler.cs
index 0619e25..524acbf 100644
--- a/NewLife.MQTT/Handlers/IMqttHandler.cs
+++ b/NewLife.MQTT/Handlers/IMqttHandler.cs
@@ -204,6 +204,7 @@ protected virtual UnsubAck OnUnsubscribe(UnsubscribeMessage message)
             QoS = qos,
         };
 
+        // 注意此处代码不要删除，是用来做消息转发给设备端之外的其他端使用的。
         if (AllowExchange)
             Exchange?.Publish(message);