I am planning to create a loosly coupled app with web services. I will be adopting the session per request method of working and storing the sessionfactory in HttpApplicationState.Application class so I can create another session from it later

The data is requested via a web service and sent to the client.

I am planning to have a before and after image of the data in the message sent to the client.

The client will manipulate the data and pass it back to the server through another web service.

On the server at this time I then have a) the original data, b) the changed data c) the original time stamp for concurrency

What I want to know is

a) does the dynamic-update = true mapping mean that nhibernate will re-read the row again to see what has changed ?

b) could I pass into a class or method my before and after images so the differences can be detected and the appropriate SQL code generated

c) would I be better off doing this myself and creating the SQL on the fly, thereby just using nhibernate for data retrevial and manually code all updates ?

d) how do I specify an additonal where clause on the update. I will have the Id column as the primary key (that the class already knows about), but where do I put the timestamp value so that is it added to the where clause i.e. UPDATE blah WHERE Id= 1 AND Concurrency = timestamp value

Many thanks

BOb

If you use select-before-update, yes. And select-before-update is almost always less efficient than just updating the row blindly. Otherwise dynamic-update means "update only those fields that you know were changed", and it only works if you're updating the object in the same session it was loaded in.



No, there isn't any such API in NHibernate.



I think you can do it in NHibernate using SaveOrUpdateCopy - you would reassociate the old object with the session (using Lock), then use SaveOrUpdateCopy(theNewObject) on the session, and commit the transaction later.



NHibernate does this automatically if you map a property using <version> or <timestamp>.