ASP.NET MVC 3 - WebDev Server Leaking Memory with Fluent NHibernate?

Question

I have an ASP.NET MVC 3 app that has an MS SQL Server 2008 remote database, connected via Fluent NHibernate. I have another app which is making various GET requests to a URL that triggers a new item being added to the database. Everytime an item is added, my local web server's memory is growing by about 100k.

    public ActionResult AddItem(string text)
    {
        using (var DatabaseSession = new FluentDatabase().Session)
            using (var tx = DatabaseSession.BeginTransaction())
            {
                Item item = DatabaseSession
                             .QueryOver<Item>()
                             .Where(x => x.Text == text)
                             .SingleOrDefault();
                if (item == null)
                       item = new ... // initialize

                item.Text = text;

                DatabaseSession.SaveOrUpdate(item);
                tx.Commit();
                DatabaseSession.Flush();
            }

        return RedirectToAction("Index");
    }

I know this isn't the ideal way to add items to a database, but this is just a test of some other functionality. After about 1000 calls to this method, the server is taking up over 1gb of data! Shortly after, I run out of memory and it crashes. It doesn't make much sense, since all of the items should be getting garbage collected. Is there something I'm missing here?

Answer 1

The easiest way to find the problem is to use some memory profiler, they will show you which objects are staying in the memory and who's holding them:

1. MemProfiler, paid, http://memprofiler.com/

2. CLR Profiler, free, Microsoft CLR Profiler for .Net 4 - http://www.microsoft.com/downloads/en/details.aspx?FamilyID=be2d842b-fdce-4600-8d32-a3cf74fda5e1 , CLR Profiler for .Net 2 and 3.5 - http://www.microsoft.com/downloads/en/details.aspx?FamilyID=a362781c-3870-43be-8926-862b40aa0cd0 . And here is a documentation for it - http://msdn.microsoft.com/en-us/library/ff650691.aspx