Why NHibernate Fills the Collection Using Projection When I Said Lazy = "True".

I am having a really hard time with NHibernate and Lazy Loading and I know many people are having the same issues. One of the other problems is that when I tell NHibernate that I was to load Users as lazy load it stills fill the Users list of the root object. This way I cannot even check for null and it always throws the NULL Exception.

The idea of having to keep the Session open while accessing the lazy load is worthless as why should I leave the session open and waste my resources.

In the code below _users is never null although lazy="true". This is because NHibernate fills it up with some projection and initialize the object.

public virtual IList<User> Users
{
get {

if (_users == null)
{
_users = UserManager.GetByExamId(this.Id);
}
return new ReadOnlyCollection<User>(_users);

}
}

Don't do any kind of tricks (i.e. checking for null/not null, wrapping, etc.) in your getters and setters. NHibernate depends on them being well-behaved.

Not sure what you meant there!

But when I only do this using NHibernate configurations then I get LazyLoadException. Here are my configuration files:

This is Exam.hbm.xml:

<bag name="Users" access="nosetter.camelcase-underscore" lazy="true" cascade="save-update" table="UserExams" >

<key column="ExamID" />
<many-to-many class="User" column="UserID" />
</bag>

Here is the Users property in the Exam.cs class.

public virtual IList<User> Users
{
get {


return new ReadOnlyCollection<User>(_users);

}
}

And here is the code:

Exam exam = ExamManager.GetById(55);

// Fails on the line below::::
Console.WriteLine(exam.Users[0].FirstName);

I meant this:

should be just:


or use access="field.blabla", not nosetter. Basically, don't confuse NHibernate.

And another thing, lazy doesn't mean the property will get initialized to null, it means the property will get initialized to a proxy (a collection proxy in this case).

Hi,

I removed the ReadOnlyCollection but it still gives me the same error.

There are just too many constraints when using NHibernate. It is like NHibernate is saying to me "It is my way or the highway".

No flexibility!

Can you show me how to make a one to many relationship where a Users collection is lazy loaded?