title: Fluent NHibernate one to many uni-directional mapping
body: <p>I have Post and Comment classes, and they have a one to many relationship where Post has a list of Comments. How can I map this as a uni-directional relationship with Fluent NHibernate, since a comment does not need to know its parent Post?  Currently, this is my mapping for Comment:</p>
  
  <pre><code>Id(x =&gt; x.Id);
  Map(x =&gt; x.Body);
  References(x =&gt; x.User);
  </code></pre>
  
  <p>and for Post:</p>
  
  <pre><code>Id(x =&gt; x.Id);
  Map(x =&gt; x.Title);
  HasMany(x =&gt; x.Comments)
      .Inverse()
      .WithKeyColumn("PostId")
      .Cascade.AllDeleteOrphan();
  </code></pre>
  
  <p>This doesnt work because when I try to save a Post instance with a newly added Comment, the foreign key on Comment (PostId) is left NULL.  And of course a comment cannot be saved with a NULL PostId.  I've tried removing the .Inverse() clause, but that doesn't work either.</p>