The part of the model that I design is the geographic location of the hierarchy. Since there are several levels and you can share some information, I decided to use the class hierarchy as follows:
public class GeographicNode
{
public virtual int Id { get; private set; }
public virtual string Name { get; set; }
public virtual GeographicNode ParentNode { get; set; }
public virtual IList<GeographicNode> ChildNodes { get; set; }
}
public class Region : GeographicNode
{
public virtual int SomeRegionData { get; set; }
}
public class Country : GeographicNode
{
public virtual int SomeCountryData { get; set; }
}
To match this, I use the table-per-class-hierarchy method. The free display of nHibernate is as follows:
public class GeographicNodeMap : ClassMap<GeographicNode>
{
public GeographicNodeMap()
{
Id(x => x.Id);
Map(x => x.Name);
References(x => x.ParentNode);
HasMany(x => x.ChildNodes).KeyColumn("Id").Cascade.All();
DiscriminateSubClassesOnColumn("Type");
}
}
public class RegionMap : SubclassMap<Region>
{
public RegionMap()
{
Map(x => x.SomeRegionData)
}
}
public class CountryMap : SubclassMap<Region>
{
public CountryMap()
{
Map(x => x.SomeCountryData)
}
}
Here is my question:
When I get a node and try to access the ParentNode (or child), its type is actually a GeographicNode, not the corresponding subclass. For example, if I get a Region node, and its parent must be a country node, I cannot use the ParentNode class for the Country class.
nHibernate ParentNode Child ? "", nHibernate .
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