Where to open and close the NHibernate ISession in a web app (specifically MVC)?

Question

This is a pretty fundamental question when using NHibernate in a web application, but I don't see any agreed best practice when searching the web. I've seen it done in lots of different places:

Created and disposed in the Repository method - This just seems silly to me, since when you get the object it's already detached.

At the beginning and end of the Controller Action - This seems better, but annoying to have to do it for each action.

At the Application level, in global.asax beginrequest and endrequest - This seems the best idea, but again, I've seen some examples creating in Init instead of beginrequest (sharp architecture for instance) - although I am not sure why.

Maybe there are other approaches?
Can IoC containers help in some way here?
Maybe you know of a good resource on the web regarding this?
And - what method do you use?

Thanks

Answer 1

Session per Request is probably the most used approach.

Answer 2

I've seen some examples creating in Init instead of beginrequest (sharp architecture for instance) - although I am not sure why.

In IIS 7 You can have access to the Session state in the Init event of Global.asax. That's why sharp arch uses beginrequest.

As for session management I agree with you - Global.asax is the best place for it. Event if you want to have a clean separation between layers and remove DAL settings from UI you can use HttpModule for it.

Also you can have a look at ayende's blog. It explains his way of session management