It seemed intuitive to make ExceptionType of type Type. Otherwise, when creating an ExceptionEvaluator you would have to set ExceptionType to an instance of the type of exception you want to trigger on. ie
ExceptionEvaluator eval = new ExceptionEvaluator();
eval.ExceptionType = new ApplicationException();
This would certainly work but ExceptionEvaluator.IsTriggeringEvent would still be comparing the type. ie
m_type.GetType() == loggingEvent.ExceptionObject.GetType()
So if the type of exception is what is being compared why not have ExceptionType be of type Type?