public class HandbookEntity
    {
        public virtual long Code {get; set }
 
        public virtual string Value { get; set; }
 
        public virtual string Remarks { get; set; }
    }

public class Entity
    {
        public virtual long Id {get; set;}
 
        public virtual string Propertry1 { get; set; }
 
        public virtual HandbookEntity HandbookEntity { get; set; }
    }

public class PrimaryKeyConvention : IIdConvention
    {
        public void Apply(IIdentityInstance instance)
        {
            instance.GeneratedBy.Native();
            instance.Column("Code");
        }
    }

public class PestMap : IAutoMappingOverride<Pest>
    {
        #region IAutoMappingOverride<Pest> Members
 
        public void Override( AutoMapping<Pest> autoMapping )
        {
            autoMapping.Id( x => x.Code ).GeneratedBy.Assigned();
        }
 
        #endregion
    }