If you are using 'System.Diagnostics.EventLog in a classlib as a class member, I would have to disagree with the others, provided you have control over the class lib. In general there is no reason to make the event log object a class member, instantiate within the function where you want to use it. The object does not have any state and little overhead, so it does not need to be a class member.
If you cannot edit the class then you must atomitize it.