Does Fluent Nhibernate Lazy loads IList from Criteria

I want to make a kind of "news feed" in the application of my company. In the scenario, User actions will generate "Activity" of different kinds, and other users will see in their "news feed".

However, an "Activity" is not related to all users, and to determine the relation, we have a complex piece of code.

Here is my Activity class

public class Activity: IActivity
{
    public virtual int Id { get; set; }
    public virtual ActivityType Type { get; set; }
    public virtual User User { get; set; }
    public virtual bool IsVisibleToUser(User userLook)
    {
        // Complex business calculation etc.
        return true;
    }
}

I want to get latest 10 news that is visible to User. But since the Activity table will be quite huge, and performance is an issue, I want to do the best practice about it.

What i am about to do, is get 25 last Activity, and check if we fill the list to show to user. For example, if only 5 Activity is visible to user, i will get another 25 Activities and so on.

IList<Activity> resultList = session.CreateCriteria(typeof(Activity))
                                .SetMaxResults(25)
                                .AddOrder(Order.Desc("Id"))
                                .List<Activity>();

I want to learn, if I get the whole list ordered by Id, and check one by one if it is visible to User, would NHibernate only loads the objects that i use for me or not?

IList<Activity> resultList = session.CreateCriteria(typeof(Activity))
                              开发者_C百科  .AddOrder(Order.Desc("Id"))
                                .List<Activity>();

int count = 0;
foreach( Activity act in resultList){
    if (act.IsVisible(CurrentUser)){
        count++;
        // Do something with act
        if (count == 10)
            break;
    }
}

EDIT: Here is ActivityMapping for Activity model.

public class ActivityMap : ClassMap<Activity>
{
    public ActivityMap()
    {
        Id(x => x.Id);
        Map(x => x.Type).CustomType(typeof(Int32));
        References(x => x.User).Nullable();
    }
}

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If your question is about how the generated SQL would look like, my guess would be :

SELECT 
   this_.Id as Id0_0_, 
   this_.ActivityTypeas ActivityType_0_0_, 
   --Other fields
FROM dbo.ActivityType this_ 
WHERE 
   --condition
ORDER BY 
   --condition

Since you have mentioned that the Activity count is huge, you can make use of ICriteria's SetFirstResult and SetMaxResult.

SetFirstResult(int) indicates the index of the first item that you wish to obtain and SetMaxResult(int) indicates the number of rows you wish to get, 25 in your case.

The ToList would load all the records in memory at once.

[UPDATE] If you need the records to be returned one by one, make use of Enumerable() -

If you expect your query to return a very large number of objects, but you don't expect to use them all, you might get better performance from the Enumerable() methods, which return a System.Collections.IEnumerable. The iterator will load objects on demand, using the identifiers returned by an initial SQL query (n+1 selects total).

Source - Link

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No, the List() method pulls everything into memory at once.