PersistentGenericBag is read only?

jhandel · **Posted:** Fri Dec 28, 2007 1:57 pm

I'm porting an app from Ayende's Generics and 1.0.3 to pure 1.2 (so removing Ayende's Generics) and am running into an issue I can't find documentation on.. (based on the few blogs that talk about this kind of porting.

I keep getting the following exception when I run my "add" routines.

System.NotSupportedException : Collection is read-only.
at System.ThrowHelper.ThrowNotSupportedException(ExceptionResource resource)
at System.Collections.ObjectModel.ReadOnlyCollection`1.System.Collections.Generic.ICollection<T>.Add(T value)
at NHibernate.Collection.Generic.PersistentGenericBag`1.Add(T item)
C:\Projects\myProject\User.cs(174,0): at MyNameSpace.UserBase.AddOwnedNode(INode node)

Below is the add routine I am using

Code:

/**** The Add Routine ****/
public void AddOwnedNode(INode node)
        {
            if (_ownedNodes.Contains(node)) return;
            _ownedNodes.Add(node);
            if (node.Owner == null)
                node.Owner = this;
            else if (!node.Owner.Equals(this))
                node.Owner = this;
        }

/**** The property & Field ****/
 private IList<INode> _ownedNodes = new List<INode>();
        public virtual IList<INode> OwnedNodes
        {
            get { return new ReadOnlyCollection<INode>(_ownedNodes); }
            set { _ownedNodes = value; }
        }

/**** The Mapping XML for this field ****/
    <bag name="OwnedNodes" lazy ="true" inverse ="true"   >
      <key column="OwnerUserFk"/>
      <one-to-many class ="MyNameSpace.INode, MyNameSpace.Interfaces"/>
    </bag>

/**** The mapping for the other side (node.Owner) ****/
<many-to-one name="Owner" class="MyNameSpace.IUser, MyNameSpace.Interfaces" column ="OwnerUserFk" not-null="true" />

Notes: I am using Interfaces and sub-classes. The technique is based on a blog post I read but goes like this

Code:

<class name="[My Interface Name]" >
   <!---- All class properties that have setters in the interface ---->
   <subclass name="[My Class Implientation name]" discriminator-value="something">
   <!---- My class properties that don't have setters in the interface ---->
   </subclass>
</class>

BUT I'm not thinking that this is related to my issue. As the maps are compiling and working fine..

Am I being stupid (My guess is yes) and PersistentGenericBag is read-only.. or am I missing something?

Thanks in advance fo the help.

Josh

jhandel · **Posted:** Mon Dec 31, 2007 1:23 pm

I realized my 1.2 dll was a little old (1.2.0) so I downloaded 1.2.1 GA BUT no luck.. my collections are still claiming to be read only.. I'm not sure whats up as my mappings (excluding my subclassing) look the same as Billy McCafferty's mappings as do my Add and Remove functions..

So anyone know why my generic collections using Default 1.2.1 nhibernate are acting all "read-only" on me?

Thanks
Josh

jhandel · **Posted:** Mon Dec 31, 2007 3:32 pm

Given enough time you will answer your own questions..

So this is what I have figured out..

NHibernate is getting my read only collection from my getter property while it is saving and/or loading the object. it then takes that read only version of my collection, wraps it in the persistantgenericbag and stuffs it back into my setter. The result is my collection becomes read only.

given that I got this methodology off of Billy McCafferty, I'm not sure how his collections don't throw the same error?

Josh

wmccafferty · **Posted:** Wed Jan 02, 2008 3:24 pm

Hi Josh,

I've released a couple of posts concerning custom collections with the latest NHibernate. I believe the new approach is much simpler than the advice I gave in my codeproject.com article.

The first in the three-part series can be found at:

http://devlicio.us/blogs/billy_mccaffer ... asics.aspx

Billy McCafferty