Question

In your MVC samples, in a controller you call Session.Demand() to get a session, then execute queries and work with entities without creating a transaction. Why? Are they automatically created by SessionManager?

Accepted Answer

1

Yes, exactly. A bit more precise info:

Session is open, when you invoke Session.Demand() for the first time in the current HttpContext. If Domain isn't build @ that time (or its previous build has failed), it will be built.
"Virtual" transaction (i.e. DO object) is created immediately, but actual transaction is only started with the first DB query. (SessionOptions.AutoShortenTransaction does this, but this properly works only in v4.4).
If no error occurs, transaction is committed. Otherwise it's rolled back. You can also control this using SessionManager properties.
AFAIK, published version has a minor bug in SessionManager: when domain build fails, it can't rebuild it on the subsequent web request. It's already fixed in repo, so the nearest update will resolve this issue. Currently you have to restart web app to get it rebuilt.

answered Dec 30 '10 at 01:42

Alex Yakunin
2971●4●4●12

A tiny addition: it's better to use the following bases for your controllers and views with MVC:

public class SessionBoundController : Controller
{
    private Xtensive.Orm.Session session;

    public HttpSessionStateBase SessionState {
        get { return base.Session; }
    }

    public new Xtensive.Orm.Session Session {
        get {
            if (session==null)
                session = Xtensive.Orm.Session.Demand();
            return session;
        }
    }
}

(Dec 30 '10 at 01:45) Alex Yakunin

And view:

public abstract class SessionBoundWebViewPage<TModel> : WebViewPage<TModel>
{
    private Xtensive.Orm.Session session;

    public HttpSessionStateBase SessionState {
        get { return base.Session; }
    }

    public new Xtensive.Orm.Session Session {
        get {
            if (session==null)
                session = Xtensive.Orm.Session.Demand();
            return session;
        }
    }
}

(Dec 30 '10 at 01:45) Alex Yakunin

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