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    <p>Your question actually boils down to object caching and reuse. If you load a Foo object from one session, then can you keep hold of it and then at a later point in time lazy load its Bar property?</p> <p>Each ISession instance is designed to represent a unit of work, and comes with a first level cache that will allow you to retrieve an object multiple times within that unit of work yet only have a single database hit. It is not thread-safe, and should definitely not be used as a static object in a WinForms application.</p> <p>If you want to use an object when the session under which it was loaded has been disposed, then you need to associate it with a new session using Session.SaveOrUpdate(object) or Session.Update(object).</p> <p>You can find all of this explained in <a href="https://www.hibernate.org/hib_docs/nhibernate/html/transactions.html" rel="nofollow noreferrer">chapter 10 of the Hibernate documentation</a>.</p> <p>If this seems inefficient, then look into second-level caching. This is provided at ISessionFactory level - your session factory can be static, and if you enable second-level caching this will effectively build an in-memory cache of much of your data. Second-level caching is only appropriate if there is no underlying service updating your data - if all database updates go via NHibernate, then it is safe.</p> <p><strong>Edit in light of code posted</strong></p> <p>Your session usage is at the wrong level - you are using it for a single database get, rather than a unit of work. In this case, your <code>GetById</code> method should take in a session which it uses, and the session instance should be managed at a higher level. Alternatively, your <code>PersonRepository</code> class should manage the session if you prefer, and you should instantiate and dispose an object of this type for each unit of work.</p> <pre><code>public T GetById(int id) { return m_session.Get&lt;T&gt;(id); } using (var repository = new PersonRepository()) { var person = repository.GetById(1); var contactInfo = person.ContactInfo; } // make sure the repository Dispose method disposes the session. </code></pre> <p>The error message you are getting is because there is no longer a session to use to lazy load the collection - you've already disposed it.</p>
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    1. COThanks for your answer. I've read the chapter from the documentation, but I still don't quite understand what you mean in the 2nd sentence. Do you mean that I have to keep hold of the session if I need to access lazy loaded properties? I'll add some of my repository code to the question.
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    2. COSure - add some context to the question and I'll address it more specifically in the answer.
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    3. CONice, thanks a lot! +1 I'll refactor my repository then :) My understanding is that the session / db stuff should be "layered away" from the actual application, so If I in addition removes it from the repository, where would I place it?
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