Question

I have come across a weird problem concerning composite keys and one-to-many relationship.

I have the following Invoice class:

public class Invoice: AccountingBase<InvoiceItem>
{
    public virtual IList<InvoiceItem> InvoiceItems {.....}
}

the class it inherits is (AccountingBase) is as follows:

public abstract class AccountingBase<TItemType>  : AccountingBase where TItemType : AccountingItemBase
{
    public virtual ObservableCollection<TItemType> Items { get; set; }

    public abstract void AddItem(TItemType item);
}

And the bottom class is:

public abstract class AccountingBase
{
    public virtual Subsidiary Subsidiary {....}
    public virtual int ID{ ....}
}

The Mapping for Invoice class is as follows:

 <class name="Invoice" table="Invoice">
     <composite-id>
       <key-many-to-one class="Subsidiary" name="Subsidiary"/>
       <key-property name="ID" column="InvoiceID" />
     </composite-id>
     <bag name="InvoiceItems" table="InvoiceItem" inverse="true" lazy="false">
       <key>
         <column name="Subsidiary" />
         <column name="InvoiceID" />
       </key>
       <one-to-many class="InvoiceItem" />
     </bag>   
 </class>

Now when i retrieve a list of Invoices it works fine, including lazily loading each Items object. The problem i get is, when i select an invoice to edit. I open a new session, and i try retrieve the same invoice using the new session, but when it loads the invoice, it doesnt load the items, it retrieves them as blank, although when i run the generated SQL manually it runs perfectly fine. What could be the reason?

The code i am running to retrieve to get the new Invoice object in the new session using the old object is:

Invoice = Session.Get<Invoice>(invoice);

When i debug, invoice is of Type Invoice, and also, invoice has 1 InvoiceItem in InvoiceItems collection, but the new instance in Invoice, all the fields are populated but the InvoiceItems is null. Is there anything i should know about Nhibernate that might cause this kind of error?

I have tried lazy="false".

Answer 1

Found the fix, i had to correctly implement Equality methods, in both Invoice class and Subsidiary class.