ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
ExchangeCredentials credentials = new WebCredentials("emailAddress", "password");
service.setCredentials(credentials);

f(g, exchange-object) {
   /* pre-condition/invariant */
   assert(exchange-object.open() == true);
   g(exchange-object);
   /* post-condition/invariant */
   assert(exchange-object.open() == true);
   }
..
f ( obj-on-the-line.g, exchange-object )
..