XML Mapping when a linked (N-To-N) table is used.

FlyTVR · **Joined:** Fri Apr 03, 2009 9:40 am **Posts:** 10

I have 3 tables.

1. Person
2. PersonToAddress (columns PersonId, AddressId and AddressType)
3. Address

PersonToAddress is a link table between Person and Address. The PersonToAddress table does not exist due to a many to many relationship, but instead it allows both a home address and alternative address to be stored alongside a person entry.

In my C# entity Person I have a property of type Address. However, I’m struggling with the XML mappings.

I can get things to sort of work using a ‘bag’ but this is not what I want. In our data model Person maps one to one to address (and vice versa). So, what should the XML mapping look like?

Apologies in advance – I’m very new to NHibernate.

Cheers FlyTVR.

wolli · **Posted:** Tue Apr 07, 2009 12:25 pm

Is home and alternative address mutually exclusiv ? Then you can use a one-to-one association between Person and PersonToAddress. If not, you need the bag. Or do you have two properties on Person, one for the home address and a second one for the optional alternative address ? In that case you can try two many-to-one associations from Person to PersonToAddress, each with a "where" clause in the mapping, which contains the constraint for the address type.

FlyTVR · **Joined:** Fri Apr 03, 2009 9:40 am **Posts:** 10

wolli wrote:

Is home and alternative address mutually exclusiv ? Then you can use a one-to-one association between Person and PersonToAddress. If not, you need the bag. Or do you have two properties on Person, one for the home address and a second one for the optional alternative address ? In that case you can try two many-to-one associations from Person to PersonToAddress, each with a "where" clause in the mapping, which contains the constraint for the address type.

I have two properties on the Person entity - HomeAddress and AlternativeAddress. Using two many-to-one associations from Person to PersonToAddress - what would the mapping look like?

Cheers.

FlyTVR

wolli · **Posted:** Wed Apr 08, 2009 2:10 am

Just checked the many-to-one. It has not "where" attribute, so my idea does not work. But in that case, I suggest you use a normal many-to-many association. You can map to a private filed/property and define two properties which retrieve the correct address from the collection.

Code:

private IList<PersonToAddress> addresses;

public Address HomeAddress { get {
     return ... find home address in list ...; } }

public Address AlternativeAddress { get {
     return ... find alternative address in list ...; } }