Using NHibernate to select entities based on activity of children entities

Posted by mannish on Stack Overflow See other posts from Stack Overflow or by mannish
Published on 2010-04-19T19:33:39Z Indexed on 2010/04/19 19:43 UTC
Read the original article Hit count: 363

Filed under:

nhibernate

I'm having a case of the Mondays...

I need to select blog posts based on recent activity in the post's comments collection (a Post has a List<Comment> property and likewise, a Comment has a Post property, establishing the relationship. I don't want to show the same post twice, and I only need a subset of the entities, not all of the posts.

First thought was to grab all posts that have comments, then order those based on the most recent comment. For this to work, I'm pretty sure I'd have to limit the comments for each Post to the first/newest Comment. Last I'd simply take the top 5 (or whatever max results number I want to pass into the method).

Second thought would be to grab all of the comments, ordered by CreatedOn, and filter so there's only one Comment per Post. Then return those top (whatever) posts. This seems like the same as the first option, just going through the back door.

I've got an ugly, two query option I've got working with some LINQ on the side for filtering, but I know there's a more elegant way to do it in using the NHibernate API. Hoping to see some good ideas here.

Related posts about nhibernate

How can I eager-load a child collection mapped to a non-primary key in NHibernate 2.1.2?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I have two objects with a many-to-many relationship between them, as follows: public class LeftHandSide { public LeftHandSide() { Name = String.Empty; Rights = new HashSet<RightHandSide>(); } public int Id { get; set; } public string Name { get; set;… >>> More
Nhibernate 2.1 and mysql 5 - InvalidCastException on Setup

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello there, I am trying to use NHibernate with Spring.Net und mySQL 5. However, when setting up the connection and creating the SessionFactoryObject, I get this InvalidCastException: NHibernate seems to cast MySql.Data.MySqlClient.MySqlConnection to System.Data.Common.DbConnection which causes… >>> More
Nhibernate transactions:Avoiding Nhibernate dependency in the service layer

as seen on Stack Overflow - Search for 'Stack Overflow'
One of practices advocated by Nhibernate experts is to do all actions in inside a transaction. In a typical 3 tier web architecture, Nhibernate depedency is limited the data layer. In such a case is it fine to use using (var tr = NHibernateSession.Current.BeginTransaction()) { at the controller… >>> More
Series of abstract classes and NHibernate

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, and first off thanks for your time to look at this. For a research project I'm working on, I have a somewhat complex design (which I've been given) to persist to a database via NHibernate. Here's an example of the class hierarchy: TransitStrategy, TransportationCompany and TransportationLocation… >>> More
Using Time columns with NHibernate, Fluent NHibernate and SQL Server 2008

as seen on Stack Overflow - Search for 'Stack Overflow'
Hello, I have a table with a time column in my SQL Server 2008 database. The property of the object I'm trying to map to is a TimeSpan. How can i tell FluentNHibernate to use the TimeAsTimeSpan NHibernate type, so that I don't have cast problems? >>> More

Developer IT