Consider the following class:

class Item
{
public int ID;
public string Name;
public IList Categories; //this is a collection of strings--category names
}

and the database schema:

CREATE TABLE Item(ID int NOT NULL, Name varchar(50) NOT NULL, CONSTRAINT PK_Item PRIMARY KEY CLUSTERED (ID ASC))

CREATE TABLE Category(ID int NOT NULL, Name varchar(50) NOT NULL, CONSTRAINT PK_Category PRIMARY KEY CLUSTERED (ID ASC))

CREATE TABLE ItemCategory(ItemID int, CategoryID INT)

ALTER TABLE [dbo].[ItemCategory] WITH CHECK ADD CONSTRAINT [FK_ItemCategory_Category] FOREIGN KEY([CategoryID])
REFERENCES [dbo].[Category] ([ID])

ALTER TABLE [dbo].[ItemCategory] CHECK CONSTRAINT [FK_ItemCategory_Category]

ALTER TABLE [dbo].[ItemCategory] WITH CHECK ADD CONSTRAINT [FK_ItemCategory_Item] FOREIGN KEY([ItemID])
REFERENCES [dbo].[Item] ([ID])

ALTER TABLE [dbo].[ItemCategory] CHECK CONSTRAINT [FK_ItemCategory_Item]

In short, there are three tables: Item, Category, and the association table ItemCategory.

The Item class has a collection of category names (strings), but NOT category objects.

What is the correct mapping in this situation? I know how to create the mapping with objects, but not with plain strings. In other words, I don't want Categories to be treated as objects, but rather just strings.

<class name="MyAssembly.Item, MyAssembly" table="Item">
<id name="ID" column="ID" type="Int32">
<generator class="identity" />
</id>
<property name="Name" column="Name" type="String" length="50"/>
<bag name="Categories" table="ItemCategory">
<key column="ItemID"/>
<many-to-one column="CategoryID" ??? /> <!--this should retrieve Category.Name from table Category-->
</bag>
</class>

See http://www.hibernate.org/hib_docs/nhibe ... s-ofvalues

Scroll down to the first example (line starting, "Some examples, first, a set of strings:...").

This does not accomplish what I am trying to do. The mapping:

<set name="Categories" table="ItemCategories">
<key column="ItemID"/>
<element column="CategoryName" type="String"/>
</set>

would work if CategoryName were stored in table ItemCategories. However, ItemCategories only has ItemID and CategoryID. CategoryName comes from table Category instead (please see my schema above).

Thanks!

Fair enough! Didn't read your question closely enough. I don't know that what you want to do is possible with vanilla config. Maybe with a custom UserType, but I'm not experienced with that.