public class class1Map : ClassMap<class1>
    {
        public class1Map()
        {
            Id(x => x.Id).GeneratedBy.GuidComb().Not.Nullable();

            Map(x => x.Date).Not.Nullable();
            // поля...

            Where("DeletionDate is null");
        }

    public class class2Map : SubclassMap<class2>
    {
        public class2Map ()
        {
            KeyColumn("Id");

            // Поля
        }
    }

    public class class3Map : SubclassMap<class3>
    {
        public class3Map ()
        {
            KeyColumn("Id");

            HasMany(x => x.Collection).AsSet().Access.CamelCaseField().KeyColumn("ColumnId").Inverse().Cascade.AllDeleteOrphan();
        }
    }

INSERT INTO dbo.[class1]
            (Date,
             ...
             Id)
VALUES      ('2012-04-04T00:00:00.00' /* @p0_0 */,
             1977 /* @p1_0 */,
             0 /* @p2_0 */,
             0 /* @p3_0 */,
             '2012-04-04T10:35:12.00' /* @p4_0 */,
             NULL /* @p5_0 */,
             1 /* @p6_0 */,
             1577 /* @p7_0 */,
             'dbad6f22-cffc-461f-a438-a02900ae7fe9' /* @p8_0 */) <- Id заполнен перед save

INSERT INTO dbo.[class2]
            (Number,
             FormId,
             Id)
VALUES      ('1977' /* @p0 */,
             1 /* @p1 */,
             'dbad6f22-cffc-461f-a438-a02900ae7fe9' /* @p2 */)

INSERT INTO dbo.[class3]
            (Id)
VALUES      ('dbad6f22-cffc-461f-a438-a02900ae7fe9' /* @p0 */)