事件聚合使用发布/订阅，集中的异常处理和线程管理

A pub/sub mediator that allows decoupled eventing to occur between service providers and service requestors. All events are invoked on a background thread managed by the event router. The user has the option to specify that the event (and the possible callback when eventing is complete) should be marshaled back to the GUI thread. The event router allows injection of actions to take before (and after) an event is invoked, as well as custom exception handling routines during event invocation. Very good write up on the benefits of event aggregator patterns - http://codebetter.com/blogs/jeremy.miller/archive/2009/07/21/braindump-on-the-event-aggregator-pattern.aspx