NHibernate Composite Key - nhibernate

Question

I have created a composite key, and it is working, but ideals I would like the separate directly fields in the row class.
The current way I'm doing this is the following:
private UserPrimaryKey _compositeKey;
public virtual UserPrimaryKey CompositeKey
{
get
{
if (_compositeKey == null) _compositeKey = new UserPrimaryKey();
return _compositeKey;
}
set {
if (_compositeKey == value) return;
_compositeKey = value;
Host = value.Host;
UserAccount = value.User;
}
}
public string Host { get; set; }
public string UserAccount { get; set; }
And i was wondering if there is any better way of doing this? Possibly in NHibernate config file.
My current config file is the follwoing:
<class name="TGS.MySQL.DataBaseObjects.DataBasePrivilege,TGS.MySQL.DataBaseObjects" table="user">
<composite-id name="CompositeKey" class="TGS.MySQL.DataBaseObjects.UserPrimaryKey, TGS.MySQL.DataBaseObjects">
<key-property name="Host" column="Host" type="string" length="60" />
<key-property name="User" column="User" type="string" length="16" />
</composite-id>
</class>

Answer 1

You can create the properties directly in your class... and map them with:
<composite-id>
<key-property name="Host"/>
<key-property name="UserAccount"/>
</composite-id>
If you do that, you'll have to override Equals and GetHashCode in your class.

Answer 2

I would suggest the following:
private UserPrimaryKey _compositeKey;
public virtual UserPrimaryKey CompositeKey
{
get
{
if (_compositeKey == null) _compositeKey = new UserPrimaryKey();
return _compositeKey;
}
set {
if (_compositeKey == value) return;
_compositeKey = value;
Host = value.Host;
UserAccount = value.User;
}
}
public string Host
{
get
{
return CompositeKey.Host;
}
set
{
CompositeKey.Host = value;
}
}
public string UserAccount
{
get
{
return CompositeKey.User;
}
set
{
CompositeKey.User = value;
}
}
This way you dont duplicate data, only return/set the data inside the composite key.

Answer 3

I would avoid the composite key when ever you can. Replace it with a regular unique constraint on both columns:
<class name="DataBasePrivilege" table="user">
<id name="id">
<generator class="hilo">
<param name="table">user_HiLo</param>
<param name="max_lo">100</param>
</generator>
</id>
<property name="Host" length="60" unique-key="user_host"/>
<property name="User" length="16" unique-key="user_host"/>
</class>
(By the way: you don't need to specify types in common cases, and you don't need to specify column names if they match the property names. This keeps you xml readable)