Illegal attempt to associate a collection with two open sessions.

These are my tables:
Users -
UserId, StateId, CityId (StateId > States.StateId, CityId > Cities.CityId)

States -
StateId, StateName

Cities -
CityId, StateId, CityName (StateId > States.StateId)

//Code
UsersRepo rUser = new UserRepo();
rUser.State = rStateRepo.Load<State>(1);
rUser.City = rCityRepo.Load<City>(1);

This does not work, am i using sessions in wrong way.???

what is lazy setting between city and state?
this exception is thrown when you try to load a same object twice in same session, and if you have lazy="false" then when you load the state cities will be automatically gets fetched. Then i your case cities are getting loaded twice.