1. XPCollection查询方式
GroupOperator go = new GroupOperator();
var classInfo = session.GetClassInfo(null, "子类FullName");
go.Operands.Add(new BinaryOperator("ObjectType", session.GetObjectType(classInfo).Oid));
var list = new XPCollection<父类>(session, go);
2.XpQuery查询方式
var addUserQuery = session.Query<父类>().OfType(子类fullName).Cast<父类>();