execute a method after dll method fired up

i want make a dll file include some methods like :

add()
edit()
list()
get()
delete()
...

so i want found out when a method fired ( something like logging ) i want every time an event in my dll fired, call a method in project ( that include dll as reference )

i can't use like this :

mydllclass.add();
mymethod();

i want a way that make it happen after all method calls ( from anywhere ) mymethod be call.

for example if edit() called inside add() method body, i want to found out that.

how should be my classes and my methods in dll ? and how can solve it ?

( or better suggestion )

thank you