public interface IDao<T, IdT>
    {
        T GetById(IdT id, bool shouldLock);       
        T Save(T entity);
        void Delete(T entity);
    }

    public interface ICustomerDao : IDao<Customer, string> { }

    public abstract class AbstractNHibernateDao<T, IdT> : IDao<T, IdT>
    {
        public T GetById(IdT id, bool shouldLock)
        {
            T entity;

            entity = default(T);

            return entity;
        }

        public T Save(T entity)
        {
            return entity;
        }

        public void Delete(T entity)
        {
            ;
        }
    }