public TopicConnectionHandler(TopicData data)
        {
            MessageReceived += DoNothing;

            // set topic data
            TopicData = data;

            // make sure handler is clear before setting a new one
            _TopicHandler = null;

            // convert subscription emum to string
            string subscriptionName = Enum.GetName(typeof(Subscriptions), TopicData.subscription);

            // assign handler
            _TopicHandler = new ServiceBusTopicHandler(TopicData.TopicConnectionString, TopicData.topic, subscriptionName, ProcessTopicMessagesAsync);
        }