OK...

I have a class 'Summary' that has an IList that holds a list of 'Project' classes, representing a one-to-many relationship. This is mapped correctly and saving a Summary causes the list of Project classes to to be saved to the database correctly as well.

The Problem: if I programmatically add a Project to the Summary class's IList, then try to save the Summary class, I get a Foriegn Key violation in my database because the Project's SummaryID field is still 0 (it never gets set)

Now, I understand that this doesn't make much sense, becuase in a normal situation, I should be able to just set the SummaryID property of the Project class when I add it to the Summary class's IList.

However, in this particular situation that will not work because I am serializing these object from XML which user's need to modify in a disconnected environment, so I am unable determine what value the database will assign for the ID fields, as I am using identities

Is there a way to get around setting the ID feilds of an object that Is being added to the collection of another object that is already in the database?

Can you just use a reference to a Summary instead of SummaryID in your Project class? And probably map summary-to-projects association using inverse="true". You will still have to ensure that projects and summaries are linked correctly after de-serialization, but it's outside the scope of NHibernate.