Ok, I have a question about cascading updates in my WinForms app. I have things setup as follows:

- Master / detail relationship (bag) with inverse="true" and cascade="all"
- In my UI, I create a session to load my object and populate UI elements, then immediately close it, giving control over to the user.
- When the user hits the Save button, I create a brand new session and call Update on my object to push changes back to the DB which all works fine.

Now, NH seems to be performing an update statement for every item in my collection, regardless of whether or not it has changed. I know that NH has no way of knowing (because I'm effectively using a brand new session to do my update) which of my items is "dirty" and therefore has to do this.

So my question is this: should I be using a disconnected session instead of a brand new session for the update? This would allow NH to determine the dirty state of the collection items and only update as necessary. Or should I be manually determining the dirty state of my children and not be relying on the cascading feature of NH?

I'd pretty much decided against disconnected sessions due to problems with stale data amongst other things. Has anyone done anything similar to this?

There is an option in your hbm.xml file that says dynamic-update=true and dynamic-insert=true.

By default these are set to false (I belive). Setting these to true will ensure that insert/update statements will only include the things that have been changed

Sorry, I've stated something you were already aware of. I've used the cascade option and it works fine for me with the dynamic-update=true.

You also want a new session for each call to the DB to avoid prolonged table locking...

My opinion is if you need to manage the state (or knowledge of the state of your objects) on your own instead of relying on the ORM tool for you, I'd advise not using that ORM tool.

Thanks for your replies...

I can definitely get this working if I use disconnected sessions (which I'm trying to avoid). I guess what I'm trying to find out is if there are any workarounds for my current method, or better still - is there anyone else out there working with the same technique in WinForms (brand new session per database interaction) - how are you handling the cascading updates?

Ok, just one more thing..

Even if I do use disconnected sessions, imagine this scenario:

I attempt a save on my model object and for some reason it throws an exception (maybe I've violated a database constraint). So I fix the problem and attempt a re-save. On this second attempt, I'm going to have to use a fresh session anyway since sessions are not exception safe. So imagine I have 100 items in my detail collection - NH will force 100 seperate updates to be pushed out to the database.

It looks as though I'm going to need a seperate mechanism for storing the dirty state of my objects, but it feels wrong somehow. Any ideas?