NHibernate JoinQueryOver on linkin Property in the other class

Question

To put it simple I have these 3 classes

class Bag { int Id; }

class Candy { int Id; }

class CandyBag
{
    int Id;
    Candy candy;
    Bag bag;
}

I need to list all Bags that contains certain type of Candy, Im THINK it goes something like this:

session.QueryOver<Bag>(() => bagAlias)
    .JoinQueryOver<CandyBag>()
        .Where(candyBag => candgyBag.Bag.Id == bagAlias.Id)
        .And(candyBag => candgBag.Candy.Id == userSelectedCandy.Id)
    .List();  

The thing is, I can't have a property of CandyBag nor Candy in the Bag class, because I have more items that a bag can hold (like Cloth/ClotheBag Food/FoodBag). And I'm saying this because I can't do

session.QueryOver<Bag>(() => bagAlias)
    .JoinQueryOver<CandyBag>(bag => bag.CandyBag, () => candyBagAlias)
        .Where(candyBag => candyBag.Bag.Id == bagAlias.Id)
    .List();  

Thanks in advance.

Answer 1

Based on your example I've created this classes:

public class Bag { 
    public int Id {get; set;} 
}
public class Candy {
    public int Id { get; set; } 
}
public class CandyBag
{
    public int Id { get; set; }
    public Candy Candy { get; set; }
    public Bag Bag { get; set; } 
}

and this NHibernate mappings

 <class name="Bag" table="Bag" lazy="false" >
        <id name="Id">
            <generator class="identity" />
        </id>
        <!--<property name="CreationDate" />-->
    </class>
    <class name="Candy" table="Candy" lazy="false" >
        <id name="Id">
            <generator class="identity" />
        </id>
        <!--<property name="CreationDate" />-->
    </class>
    <class name="CandyBag" table="CandyBag" lazy="false" >
        <id name="Id">
            <generator class="identity" />
        </id>
        <many-to-one name="Candy" column="CandyId" lazy="false" />
        <many-to-one name="Bag" column="BagId" lazy="false" />
    </class>

To obtain Bag collection of a certain Candy:

IList<Bag> bags = null;
using (var session = OpenSession())
{
    CandyBag candyBagAlias = null;
    bags = session.QueryOver<CandyBag>(() => candyBagAlias)     
        .Where(() => candyBagAlias.Candy.Id == userSelectedCandyId )
        .List()
        .Select(cb => cb.Bag).ToList();

    // or with LINQ
    bags = (
        from bag in session.Query<Bag>()
        join candyBag in session.Query<CandyBag>() on bag equals candyBag.Bag
        where candyBag.Candy.Id == userSelectedCandyId 
        select bag 
    ).ToList();
}
return bags;

I prefer the LINQ way because it is really simple to understand.