Many-to-One with fixed values for a missing column

Question

I'm dealing with a legacy database that has a locked schema. The problem I'm facing is that a number of the tables are keyed off known/fixed/hard-coded entity type Id values instead of having a column values. This means that I can't use the normal References construct.

For the tables with the ENTITY_TYPEID I can do this:

public class EntityMap : ClassMap<Entity>
{
   public EntityMap()
   {
      References(x => x.Type)
         .Columns("ENTITY_SECTION","ENTITY_TYPEID");
   }
}

which happily populates the Entity.Type.

For the tables of a fixed/known/hard-coded type I need to map to a hard-coded value instead of the ENTITY_TYPE column, so to para-phrase in code:

public class EntityXMap : ClassMap<EntityX>
{
   public EntityXMap(int entityType)
   {
      References(x => x.Type)
         .Columns("ENTITY_SECTION", "ENTITY_TYPE = 123" );
   }
}

HasMany() has a Where() construct that I could use in that case...

Any ideas how to achieve something similar here?

Answer 1

maybe overkill but you could try

// add to config
var typemap = new TypeMap();
typemap.Id(x => x.Section, "ENTITY_SECTION");
typemap.Where("ENTITY_TYPE = 123");
typemap.EntityName("Type for EntityX");

References(x => x.Type)
   .Column("ENTITY_SECTION")
   .EntityName("Type for EntityX");