I am working with a standard parent-child relationship. I have noticed that when adding a child to the parent's children collection as described in the documentation under "Example:Parent/Child", the entire collection is completely initialized. Is there any way to prevent this? Since NHibernate is using a proxy for collections, it seems like it could be possible to avoid initializing the entire collection when an item is added.

Is there any way to avoid this hit? Do I have any alternatives?

All collections except bags are required to return some value from their Add method to indicate whether the addition was successful or what is the position of the new item. Bags are an exception and calling Add on an IList mapped as a <bag> will not cause it to initialize.

A bag did not initialize the collection on an add, so that is good, but an add of a child with a bag mapping doesn't seem to be updating the version of the parent item. Is this by design?

The version should get updated at commit. If it isn't then it's a bug.

I have verified, the version is not getting updated on an add to the collection. However, an insert into a specific index does cause the parent's verison to update, and a remove from the collection also causes the parent's version to update.

Should I log this as a bug?