Hi,
I get this error when trying to save an aggregate root item with Merge. The
item is read with Fluent NHibernate. Since I'd like to bind the data to the
WPF user interface, I use a custom getter/setter to transform collections
(IList<>) to ObservableCollections.
This is the mapping:
RootItemMap() {
Id(x => x.Id);
Map(x => x.Description);
HasMany<ChildItem>(x =>
x.Children).Access.Using<ObservableAccessor<ChildItem>>().KeyColumn("RootId").Cascade.All();
}
And this is the Set method of the custom accessor:
public void Set(object target, object value)
{
var collection = new
ObservableCollection<T>((IList<T>)value);
_property.SetValue(target, collection, null);
}
This works fine in on the client. I can add and remove items and the UI
responds fine. But when I try to save the changes with session.Merge I get
the above exception.
Any ideas? If I add a Try-Catch in the Set method this works just fine.
Here is a test class that illustrates the fault (ThenItCanBeSavedWithMerge
causes the error):
namespace MergeProblem.Tests
{
[TestFixture]
public class WhenWorkingWithRootItemWithChildren
{
private int _id;
private RootItem _root;
[TestFixtureSetUp]
public void AddRootWithChildrenToDatabase()
{
var root = new RootItem();
root.Description = "My decription";
IList<ChildItem> children = new
ObservableCollection<ChildItem>() { new ChildItem() { Description = "First
child" }, new ChildItem() { Description = "Second child"}};
root.Children = children;
using (var session = SessionManager.GetSession())
{
using (var tx = session.BeginTransaction())
{
session.SaveOrUpdate(root);
tx.Commit();
}
_id = root.Id;
_root = root;
}
}
[Test]
public void ThenItCanBeAccessed()
{
using (var session = SessionManager.GetSession())
{
var root = session.Get<RootItem>(_id);
Assert.IsNotNull(root, "Root is null");
Assert.AreEqual(_id, root.Id, "Id incorrect");
Assert.IsNotNull(root.Children, "Children is null");
Assert.AreEqual(2, root.Children.Count);
}
}
[Test]
public void ThenTheChildrenCollectionIsObservable()
{
Assert.That(_root.Children,
Is.InstanceOf(typeof(INotifyCollectionChanged)), "We want the collection to
be observable");
}
[Test]
public void ThenItCanBeSavedWithMerge()
{
var newChild = new ChildItem() { Description = "New child" };
_root.Children.Add(newChild);
using (var session = SessionManager.GetSession())
{
using (var tx = session.BeginTransaction())
{
_root = session.Merge(_root);
tx.Commit();
}
}
Assert.AreEqual(3, _root.Children.Count);
}
}
}
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