Callbacks in Composite Application Block

below code sa开发者_如何学JAVAys I can not convert from void to bool, thats ok but how can I define a callback for a fired event in CAB ?

internal bool IsÖrtlichkeitFocused()
    {
      return this.WorkItem.EventTopics[EventTopicNames.IsOertlichkeitFocusChanged].Fire(this, new EventArgs<bool?>(null), this.WorkItem, PublicationScope.WorkItem);             
    }

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try this [EventSubscription(EventTopicNames.IsOertlichkeitFocusChanged, ThreadOption.WorkItem)] public void IsÖrtlichkeitFocusedEventHandler(object sender, EventArgs e) { //do something }