Clever Geek Handbook

NHibernate - Get a parent with a logged out child collection

I am currently working on writing a very simple online forum, and I want to get a stream with a child collection of posts to be uploaded. So my mappings:

<class name="Thread" table="ForumThreads">
    <id name="Id">
        <generator class="identity"></generator>
    </id>

    <property name="Title"></property>

    <bag name="Posts">
        <key column="ThreadID"></key>
        <one-to-many class="Post"/>
    </bag>
</class>

<class name="Post" table="ForumPosts">
    <id name="Id">
        <generator class="identity"></generator>
    </id>

    <property name="Content"></property>

    <many-to-one name="Thread"
                 class="Thread"
                 column="ThreadID">
    </many-to-one>
</class>

And I want to do something like this:

public class Thread
{
    public virtual int Id { get; set; }
    public virtual string Title { get; set; }
    public virtual IEnumerable<Post> Posts { get; set; }
}

public class Post
{
    public virtual int Id { get; set; }
    public virtual Thread Thread { get; set; }
    public virtual string Content { get; set; }
}

public Thread GetThread(int threadId, int page, int pageSize, out int count)
{
    var session = SessionFactory.CurrentSession;

    // Query to get the thread with a child collection of paged posts. 

    return thread;
}

Is it possible to do this with a single query, or will I have to split it in two?

thank

+3


source to share


2 answers 


var threadId = ...
session.QueryOver<Thread>
  .Where(thread => thread.Id == threadId)
  .Fetch(thread => thread.Posts).Eager
  .Take(pageSize)
  .Skip(page)
  .TransformUsing(Transformers.DistinctRootEntity)
  .List<Thread>();


+3


source


If you are thinking about doing db level paging then the approach would be something like this,



  • You must use a collection to support lazy loading with extra mode

  • You may need to use a filter to load the collection (but you cannot return a stream as a result, as if you tried to access the collection it will load all messages)

    public List<Post> GetThreadPosts(int threadId, int page, int pageSize, out int count)
{
    var session = SessionFactory.CurrentSession;
     Thread thread = (Thread )session.Get(typeof(Thread ), threadId);
     var posts = session.CreateFilter(thread .Posts, "").SetFirstResult((page - 1)  * pageSize).SetMaxResults(pageSize).List();

    return posts ;
}
0


source






More articles:


All Articles