Mapping One to One in FluentNHibernate, NHibernate tries to write child before parent - nhibernate

Question

I'm trying to do a 1:1 relationship in FN but its being a bit of a pain.
I looked at http://avinashsing.sunkur.com/2011/09/29/how-to-do-a-one-to-one-mapping-in-fluent-nhibernate/ which seemed to confirm this should work but hey ho, it keeps trying to insert records into the child tables before the parent which means the child-inserts dont contain the CustomerId which is required as its a foreign key constraint.
Tables
+-----------------------+ +----------------------+
| tblCustomer | | tblCustomerPhoto |
|-----------------------| |----------------------|
| | 1:1 | |
| CustomerID (PK) |+---->| CustomerID (FK) |
| OtherJunk... | | Photo (Image) |
| | | |
| | | |
+-----------------------+ +----------------------+
Models
public class Customer
{
public virtual int CustomerID { get; private set; }
/* public virtual Other stuff */
}
public class CustomerPhoto
{
public virtual int CustomerID { get;set;}
public virtual Byte[] Photograph { get; set; }
}
Maps
public class CustomerPhotoMap : ClassMap<CustomerPhoto>
{
public CustomerPhotoMap()
{
Id(x => x.CustomerID)
.Column("CustomerID")
.GeneratedBy.Assigned();
Map(x => x.Photograph)
.CustomSqlType("Image")
.CustomType<Byte[]>()
.Nullable();
}
}
public class CustomerMap : ClassMap<Customer>
{
public CustomerMap()
{
Id(x => x.CustomerID)
.GeneratedBy.Identity()
.Column("CustomerID");
HasOne<CustomerPhoto>(x => x.CustomerPhoto)
.LazyLoad()
.ForeignKey("CustomerID");
}
}
Test
class CustomerMappingFixture : IntegrationTestBase
{
[Test]
public void CanMapCustomer()
{
new PersistenceSpecification<Customer>(Session)
.CheckReference(x => x.CustomerPhoto, new CustomerPhoto(){ Photograph = Arrange.GetBitmapData(ImageFormat.Jpeg) })
.VerifyTheMappings();
}
}
Now the foreign key column on the CustomerPhoto was set to not-null and I was repeating this in the notation on the CustomerPhotoMapping.
On the basis of ( https://stackoverflow.com/a/2286491/529120 ) I changed that to nullable and removed the notation from the mapping.
Regardless of which, NHibernate returns
System.NullReferenceException : Object reference not set to an instance of an object.
and appears to be trying to insert a CustomerPhoto record first, passing zero as the CustomerId; then creating the Customer record, then trying to select the customer and photo using a left outer join. Which obviously wont work as at no point has it attempted to update the ID in the photo table.

Answer 1

Few things I noticed
Using CheckReference to verify this mapping is probably incorrect. I'm pretty sure this is only for many-to-one relationships. Therefore it makes sense that it's trying to insert the CustomerPhoto before the Customer. I would write a test using straight up NH sessions here. I found it to be more trouble than it's worth to use PersistenceSpecification for many of my mappings that were non-trivial.
The one to one mappings looked like they were a bit off (proposed solution below)
When mapping an image column to a byte array I don't think there is a need to declare a custom type. The mapping below has worked fine for me. I think the other stuff you have on that property mapping is un-needed.
I have a mapping almost identical to yours and this is what I use:
public class Customer
{
public virtual int CustomerID { get; private set; }
public virtual CustomerPhoto CustomerPhoto { get; set; }
/* public virtual Other crap */
}
public class CustomerPhoto
{
public virtual Customer Customer { get; set; }
public virtual Byte[] Photograph { get; set; }
}
public class CustomerPhotoMap : ClassMap<CustomerPhoto>
{
public CustomerPhotoMap()
{
Id(x => x.Id)
.Column("CustomerID")
.GeneratedBy.Foreign("Customer");
Map(x => x.Photograph).Length(Int32.MaxValue);
}
}
public class CustomerMap : ClassMap<Customer>
{
public CustomerMap()
{
Id(x => x.CustomerID).GeneratedBy.Identity()
.Column("CustomerID");
HasOne(x => x.CustomerPhoto)
.Cascade.All();
}
}