CODEWITHSUNDEEP
nhibernatetransactions
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Reputation: 5379

NHibernate - Best Practice for just select

A have an action on my MVC application that have an id and returns a person's name.

What is the best practice for that? I'm following NHProf tips, but code sounds a little strange or something for me.

using (var session = Helper.SessionFactory.OpenStatelessSession())
{
    using (var tran = session.BeginTransaction(IsolationLevel.ReadCommitted))
    {
        return session.Query<Person>().Where(x => x.Id == id).Select(x => x.Name).SingleOrDefault();
        tran.Rollback();
    }
}

Upvotes: 5

Views: 4290

Answers (3)

Baz1nga
Baz1nga

Reputation: 15579

do not create multiple sessions over one HTTP request, ideally what you need to do is open a session and a corresponding transaction at the request scope and use this session throughout all your actions.

Here is a blogpost explaining how to achieve it: http://hackingon.net/post/NHibernate-Session-Per-Request-with-ASPNET-MVC.aspx

I would suggest the use of an IOC container and create a class that creates the session for you and scope this class to the request scope.

There are lots of resources on the web to approach this problem.. Google it..

Upvotes: 0

Peadar Doyle
Peadar Doyle

Reputation: 1112

The following is how I would approach this select:

    using (var session = Helper.SessionFactory.OpenStatelessSession())
    using (var tran = session.BeginTransaction(IsolationLevel.ReadCommitted))
    {
        try
        {
            string personName = session.Query<Person>()
            .Where(x => x.Id == id)
            .Single(x => x.Name);

            tran.Commit();
            return personName;
        }
        catch(Exception ex)
        {
            // handle exception
            tran.Rollback();
        }
    }

This SO answer gives good advice to dealing with transaction commits:

NHibernate - Is ITransaction.Commit really necessary?

With regards to your LINQ this is an interesting article on how not to approach queries using the extension method style syntax:

http://compiledexperience.com/blog/posts/how-not-to-use-linq

Upvotes: 0

richeym
richeym

Reputation: 4079

The NHProf alert page explains it quite well I think -

http://nhprof.com/Learn/Alerts/DoNotUseImplicitTransactions

Basically it's saying if you don't manage transactions yourself, the database will create an "implicit transaction" and auto-commit for every statement, including queries. The misconception is that transactions are useful only for insert / update operations.

In your example above, it's not much of an issue as your transaction only executes a single statement anyway. If your method was running several statements however it would be good practice to wrap them in a transaction.

Upvotes: 4

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