NHibernate - Generate Id from seed table

Recently I came across a problem where I had to auto generate entity Id by using seed table of database. I was not allowed to keep auto generate at database level.  I was using NHibernate ORM.

Scenario:

I have a seed table.

   Table : Seed

   Columns :

            1.       TableName

            2.       LastId
      I have to use this table to create id for other tables. I was looking a better way to accomplish this.

Solution :

            1.       Create a seed generator class - NHibernate gives an interface IIdentifierGenerator which really helps lot. It gives a signature to use and pass id.

namespace SimpleNHibernateClient.ConsoleApplication

{

    using NHibernate.Id;

    /// <summary>

    /// Seed Generator

    /// </summary>

    public class SeedGenerator<T> : IIdentifierGenerator

    {

        public object Generate(NHibernate.Engine.ISessionImplementor session, object obj)

        {

            return 1;/* Take it from seed table corresponding T. */

        }

    }

}

          2.       Entity Class-This is a entity class to be saved into database.

namespace SimpleNHibernateClient.ConsoleApplication

{

    public class Student

    {

        public virtual int Id { get; set; }

        public virtual string Name { get; set; }

    }

}

         3.       Mapping Class-This is a mapping class to be used for mapping and calling seed generator.

namespace SimpleNHibernateClient.ConsoleApplication

{

    using FluentNHibernate.Mapping;

    public class StudentMap : ClassMap<Student>

    {

        public StudentMap()

        {

            Table("Student");

            Id(x => x.Id, "Id").GeneratedBy.Custom<SeedGenerator<Student>>();

            Map(x => x.Name, "Name");

        }

    }

}

Now it gets generated by Generate Method.