linqnhibernatelinq-to-nhibernatequeryover

NHibernate 3.0: No FirstOrDefault() with QueryOver?

I am playing with FluentNHibernate and NH 3.0, using the LINQ provider and the new QueryOver syntax.

Now with QueryOver I want to get an item (called result) with a timestamp value as close as possible to a given value, but not greater:

 Result precedingOrMatchingResult = Session.QueryOver<Result>().
        Where(r => r.TimeStamp < timeStamp).
        OrderBy(r => r.TimeStamp).Desc.                
        FirstOrDefault(); //get the preceding or matching result, if there is any

Now, Intellisense tells me that there is no such thing as a FirstOrDefault() method. I could, of course, enumerate my ordered query, and then use LINQ to get my item. But this would load all items into memory first.

Is there an alternative to FirstOrDefault(), or have I understood something completely wrong?

Solution

  • NH 3 has an integrated LINQ provider (queries are translated internally to HQL/SQL). You have to add the NHibernate.Linq namespace and then:

    Result precedingOrMatchingResult = Session.Query<Result>().
    Where(r => r.TimeStamp < timeStamp).
    OrderByDescending(r => r.TimeStamp).
    FirstOrDefault();