how to unsubscibe all topics

[lujiashun1]

MqttTest.zip `var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()

            .Build();
        //MqttClientUnsubscribeOptions mqttClientUnsubscribeOptions = new MqttClientUnsubscribeOptions();
        //mqttClientUnsubscribeOptions.TopicFilters = mqttClient.Options.
        //await mqttClient.UnsubscribeAsync(mqttClientUnsubscribeOptions);
        mqttSubscribeOptions.TopicFilters = mqttTopicFilters;


        var response = await mqttClient.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);`

when I click Subscribe several times，I received several identical messages at the same time, Can't it remove duplicate topics,or how to unsbuscribe all topics?