Nhibernate composite key question - nhibernate

Question

I have a table called person_skills like so:
person_id, skill_type_id, base_score, misc_score
There is a lookup table that contains id, name for skill_types.
Now the tricky thing is that I have a composite key for person_id, skill_type_id. There will be many entries within this table as a person may have 5 skills.
Currently I have got a class like so:
public class skill
{
int BaseScore {get;set;}
int MiscScore {get;set;}
}
Then I have a class to contain all this like below:
public class person_skills
{
int person_id {get;set;}
IDictionary<skill_type, skill> skills {get;set;}
}
Now im not sure if this is the best way to handle this relationship, ultimately I need to be able to give people a link to skills, there is one person to many skills.
I was thinking about just putting in an auto incrememnt id column and use that as the PK, but it doesn't seem ideal. I can change the models and the DB if required, but as this is used within an ajax part of a page I need to be able to change the skills and then update them into the database.

Answer 1

I did not find an actual question but I'll answer anyway. :)
You do not need a surrogate key for the person_skills table. Your composite key, consisting of person_id and skill_type_id, should be sufficient. I believe the following classes and mappings reflect what you are trying to accomplish here.
Classes:
public class Person
{
public virtual int PersonId { get; set; }
public virtual String Name { get; set; }
public virtual IList<PersonSkills> Skills { get; set; }
}
public class SkillType
{
public virtual int SkillTypeId { get; set; }
public virtual String SkillName { get; set; }
public virtual IList<PersonSkills> Persons { get; set; }
}
public class PersonSkills
{
public virtual int PersonId { get; set; }
public virtual int SkillTypeId { get; set; }
public virtual int BaseScore { get; set; }
public virtual int MiscScore { get; set; }
public override bool Equals(object obj)
{
if (ReferenceEquals(this, obj))
{
return true;
}
if (obj == null || !(obj is PersonSkills))
{
return false;
}
PersonSkills o = obj as PersonSkills;
return (this.PersonId == o.PersonId
&& this.SkillTypeId == o.SkillTypeId);
}
public override int GetHashCode()
{
int hash = 13;
hash = hash + this.PersonId.GetHashCode();
hash = hash + this.SkillTypeId.GetHashCode();
return hash;
}
}
Mappings: (FluentNhibernate)
public class PersonMap : ClassMap<Person>
{
public PersonMap()
{
Id(x => x.PersonId);
Map(x => x.Name);
HasMany(x => x.Skills)
.KeyColumn("PersonId")
.Cascade.All();
}
}
public class SkillTypeMap : ClassMap<SkillType>
{
public SkillTypeMap()
{
Id(x => x.SkillTypeId);
Map(x => x.SkillName);
HasMany(x => x.Persons)
.KeyColumn("SkillTypeId")
.Cascade.All();
}
}
public class PersonSkillsMap : ClassMap<PersonSkills>
{
public PersonSkillsMap()
{
CompositeId()
.KeyProperty(x => x.PersonId)
.KeyProperty(x => x.SkillTypeId);
Map(x => x.BaseScore);
Map(x => x.MiscScore);
}
}
Mappings (hbm, generated by FluentNHibernate - I removed output that is not required):
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" >
<class xmlns="urn:nhibernate-mapping-2.2" name="Person" table="Person">
<id name="PersonId" type="int">
<column name="PersonId" />
<generator class="identity" />
</id>
<bag cascade="all" name="Skills" mutable="true">
<key>
<column name="PersonId" />
</key>
<one-to-many class="PersonSkills" />
</bag>
<property name="Name" type="String">
<column name="Name" />
</property>
</class>
</hibernate-mapping>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" >
<class xmlns="urn:nhibernate-mapping-2.2" name="SkillType" table="SkillType">
<id name="SkillTypeId" type="int">
<column name="SkillTypeId" />
<generator class="identity" />
</id>
<bag cascade="all" name="Persons">
<key>
<column name="SkillTypeId" />
</key>
<one-to-many class="PersonSkills" />
</bag>
<property name="SkillName" type="String">
<column name="SkillName" />
</property>
</class>
</hibernate-mapping>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" >
<class xmlns="urn:nhibernate-mapping-2.2" name="PersonSkills" table="PersonSkills">
<composite-id mapped="false" unsaved-value="undefined">
<key-property name="PersonId" type="int">
<column name="PersonId" />
</key-property>
<key-property name="SkillTypeId" type="int">
<column name="SkillTypeId" />
</key-property>
</composite-id>
<property name="BaseScore" type="int">
<column name="BaseScore" />
</property>
<property name="MiscScore" type="int">
<column name="MiscScore" />
</property>
</class>
</hibernate-mapping>