Persist a top-level collection?

Question

NHibernate allows me to query a database and get an IList of objects in return. Suppose I get a list of a couple of dozen objects and modify a half-dozen or so. Does NHibernate have a way to persist changes to the collection, or do I have to persist each object as I change it?

Here's an example. Suppose I run the following code:

var hql = "from Project";
var query = session.CreateQuery(hql);
var myProjectList = query.List<Project>();

I will get back an IList that contains all projects. Now suppose I execute the following code:

var myNewProject = new Project("My New Project");
myProjectList .Add(myNewProject);

And let's say I do this several times, adding several new projects to the list. Now I'm ready to persist the changes to the collection.

I'd like to persist the changes by simply passing myProjectList to the current ISession for updating. But ISession.SaveOrUpdate() appears to take only individual objects, not collections like myProjectList. Is there a way that I can persist changes to myProjectList, or do I have to persist each new object as I create it? Thanks for your help.

David Veeneman
Foresight Systems

Answer 1

If you load objects like in your example - then yes you have to persist them one by one.

However, if you make a small design change, and load something like : Account that has an IList<Project> - if you specify cascade "what_cascade_you_need" in the mapping , then when you change the projects on Account , you only have to save Account and everything will get saved.