public BaseActivityContext BuildContext(UserActivity activity, BaseAggregation aggregation)
 {
     var aggr = aggregation as UpdateAggregation;
       return new UpdateActivityContext(activity, aggr.CurrentEvent, aggr.PreviousEvent);
 }
 public BaseActivityContext BuildContext(UserActivity activity, BaseAggregation aggregation)
 {
     return new BaseActivityContext(activity, aggregation.CurrentEvent);
 }