Fluent Nhibernate foreign key constraint -

i have problem fluent nhibernate mapping.

say have 2 entities b this:

public class {     public virtual guid id { get; private set; }     public virtual b reftob { get; set; } }  public class b {     public virtual guid id { get; private set; } } 

how should map them, forbid me delete b when it's referenced a.

so, when i'm going say:

b b = new b(); a = new a(); a.reftob = b; session.save(b); session.save(a); 

(...)

session.delete(b); //should throw kind of exception states                     //"cannot remove b used a" 

first need figure out kind of relationship have. go link useful information on one-to-one relationship mapping - if want:

http://brunoreis.com/tech/fluent-nhibernate-hasone-how-implement-one-to-one-relationship/