How to handle NHibernate's "where" mappings?

[Kevin Pang]

Let's say I have an e-commerce application where a User can have
multiple Orders. Let's say that in this domain, a User can cancel his/
her Order which changes its status from "Pending" to "Canceled". The
only thing that distinguishes a "Pending" Order from a "Canceled"
Order in the database is this status flag.

Now, let's say that "Canceled" Orders don't need to be displayed too
often. It seems reasonable that my User object might want two lazy-
loaded lists, one for the User's "Pending" Orders and one for the
Users's "Canceled" Orders. It sounds like I can do this using the
"where" attribute on the "map" element of my NHibernate mappings
(basically having two one-to-many

If I wanted my domain model to contain, say, a lazy-loaded list for
his current Orders as well as a lazy-loaded list of his past Orders,
would that be possible using NHibernate?

Secondly, if it is possible and I wanted to add a "CancelOrder"
function to my User class, what would it do? Looking at it from the
domain's perspective, it feels like I should find the correct Order
from the "Pending" list, change its status to "Canceled", and move it
to the "Canceled" list. Will NHibernate be smart enough to figure out
how to persist that?

[Jason Meckley]

filters is the way to go here. you can (dis)enable them per session to
get a clean domain. Where clauses are permanent, filters are not.
there is an article or 2 on nhforge wiki about filters. ayende and
fabio (i think) also have posts about filters on their respective
blogs.

another option is to have a separate entities for orders. I have heard
of this approach with larger e-commerce models. instead of a status
flag and property to determine the status of the order, you have
entire entity aggregates for each of the different statuses. each
status has it's own set of behavior that is completely independent of
the other statuses. they are usually something like
Shopping Cart
Order
Invoice
CancelledOrder