Set identity seed in fluentnhibernate - fluent-nhibernate

Question

Using NHibernate you can set an identity seed like so:
<column name="Column1" not-null="true" sql-type="int IDENTITY(1,1000)"/>
The FluentNHibernate IdentityPart has CustomType and SqlCustomType methods, neither does it for me though. Is there a way to fluently set an identity seed?
More info:
When I do this: Map(x => x.Id).Column("CustomerId").CustomSqlType("int IDENTITY(1,1000)");
I get this error: The entity 'Customer' doesn't have an Id mapped. Use the Id method to map your identity property. For example: Id(x => x.Id).
When I do this: Id(x => x.Id).Column("CustomerId").CustomSqlType("int IDENTITY(1,1000)");
I get this error: More than one column IDENTITY constraint specified for column 'CustomerId', table 'Customer'
Using FluentNHibernate 1.2.0.712.

Answer 1

I was able to duplicate that xml by doing something like this:
Map(x => x.LoginName, "Column1").CustomSqlType("int IDENTITY(1,1000)");
Edit:
If you can't achieve what you are wanting maybe you should explicitly map this using xml for now.

Answer 2

There is the article at the link below about implementing custom identity generator (see: Part 1: Inheriting from TableGenerator class) but the example throws the exception for SQLite database ("SQLite errorr no such table: hibernate_unique_key"). Thus as regard SQLite there is no possibility to gain current id key from a table. It uses class TableGenerator from NHibernate API (NHibernate.Id);
http://nhforge.org/wikis/howtonh/creating-a-custom-id-generator-for-nhibernate.aspx
To avoid the exception I implemented another solution (especially the way of getting current Id). It takes advantage of Fluent-NHibernate API (GeneratedBy.Custom()). Look at the following source code:
public class MyAutoincrement<T> : IIdentifierGenerator where T : IId
{
#region IIdentifierGenerator Members
public object Generate(ISessionImplementor session, object obj)
{
NHibernate.ISession s = (NHibernate.ISession)session;
int seedValue = 1000;
int maxId = -1;//start autoincrement from zero! (fluent nhibernate start from 1 as default)
List<T> recs = s.Query<T>().ToList<T>();
if (recs.Count > 0)
{
maxId = recs.Max(x => x.getId());
}
return seedValue + maxId + 1;
}
#endregion
}
//Interface for access to current Id of table
public interface IId
{
int getId();
}
//Entity
public class MyEntity : IId
{
public virtual int Id { get; protected set; }
public virtual string MyField1 { get; set; }
public virtual string MyField2 { get; set; }
#region IId Members
public virtual int getId()
{
return this.Id;
}
#endregion
}
//Entity Mapping
public class MyEntityMap : ClassMap<MyEntity>
{
public MyEntityMap()
{
Id(x => x.Id).GeneratedBy.Custom<MyAutoincrement<MyEntity>>();
Map(x => x.MyField1);
Map(x => x.MyField1);
}
}
It works with SQLite database and involves custom identity seed.
Regards
Bronek