Question

I have a Table called Product and I have the Table StorageHistory.

Now, Product contains a reference to StorageHistory in it’s mappings

<set name='StorageHistories' lazy='false'>   <key column='ProductId' />   <one-to-many class='StorageHistory' /> </set> 

And it works, when I retrieve an object from the ORM I get an empty ISet.

What gives me a headache is how to construct the object in the first place. When I do the following:

var product = new Product(); session.Save(product); 

the product.StorageHistories property is NULL and I get a NullReferenceException. So, how do I add items to that collection, or should I go the way to add the StorageHistory items themselves to the DB?

Answer 1

I always do the following in the ctor of the parent object:

histories = new HashedSet();

This covers the Save() use case. The Load()/Get() etc usecase is covered by NHibernate as you stated.