I am not accessing the UI Element. I am only removing from the datasource .  Can you give me sample if what i am doing below is not what you are referrring to

Please see the piece of code

Here ParentColl is the datasource. 

       ObservableCollection<TreeElement> ParentColl;

       TreeElement Parent =  ParentColl[1];

       TreeElement ChildItem = Parent.Children.FirstOrDefault();

       Parent.Children.Remove(ChildItem);

Xaml:

<ig:XamDataTree x:Name="MyTree" AllowDrop="True" DisplayMemberPath="Name" ItemsSource="{Binding ParentColl}">
    <ig:XamDataTree.GlobalNodeLayouts>
       <ig:NodeLayout Key="ParentLayout" TargetTypeName="TreeElement" IsDraggable="True" IsDropTarget="True" DisplayMemberPath="Name"/>
    </ig:XamDataTree.GlobalNodeLayouts>
</ig:XamDataTree>

Adding the Class for Parent for your reference:

public class TreeElement

{
     private ObservableCollection<TreeElement> _childNodes;

     public string Name { get; set; }

     public ObservableCollection<TreeElement> Children
    {
        get
         {
             if (this._childNodes == null)
             this._childNodes = new ObservableCollection<TreeElement>();

            return this._childNodes;
         }
    }

}

Hello Vetriselvan,

I have put together a sample project using the code snippets you shared. The child node of the second parent is deleted when the user clicks the Delete button. Since in the code snippet the item is removed from the source collection, the XamDataTree node is deleted without any exceptions.

Please feel free to use the sample project as a starting point when implementing this functionality. And do not hesitate to let me know if you have any questions or concerns.

I just ran the sample without any modification as you have given.

The same exception "Object reference not set to an instance of an object" occurs at the line

Parent.Children.Remove(ChildItem);

   at Infragistics.Controls.Menus.NodeLayout.UnSubscribeForNotificationsForNodeData(Object nodeData)
   at Infragistics.Controls.Menus.NodesManager.DataManager_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   at Infragistics.DataManagerBase.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at Infragistics.DataManagerBase.OnDataSourceCollectionChanged(NotifyCollectionChangedEventArgs e)
   at Infragistics.DataManager`1.OnDataSourceCollectionChanged(NotifyCollectionChangedEventArgs e)
   at Infragistics.DataManagerBase.<SetDataSource>b__9(DataManagerBase instance, Object s, NotifyCollectionChangedEventArgs e)
   at Infragistics.WeakEventHandler`3.OnEvent(Object source, TEventArgs eventArgs)
   at System.Collections.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)
   at System.Collections.ObjectModel.Collection`1.Remove(T item)
   at XamDataTreeDeleteNode.MainWindow.btnDelete_Click(Object sender, RoutedEventArgs e)

I guess the child element is not available as virtualization is on

Is there any way you can turn off virtualization by a flag?

Let me know if any solution is there

Adding the Version I am Using

16.1.20161.2056

RunTime Version : v4.0.30319

Are we both using the same version?

Hello Vetriselvan,

The NullReferenceException which occurred when removing a node and is reproduced with 16.1.20161.2056 has already been fixed internally and will be included in the next service release. I have linked this case to Development Issue 221815 so that you will be notified when the service release is available.

Let me know if you have any questions.

We've encountered the same issue:

Stack below:

   at Infragistics.Controls.Menus.NodeLayout.UnSubscribeForNotificationsForNodeData(Object nodeData)

   at Infragistics.Controls.Menus.NodesManager.DataManager_CollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)

   at Infragistics.DataManagerBase.OnCollectionChanged(NotifyCollectionChangedEventArgs e)

   at Infragistics.DataManagerBase.OnDataSourceCollectionChanged(NotifyCollectionChangedEventArgs e)

   at Infragistics.DataManager`1.OnDataSourceCollectionChanged(NotifyCollectionChangedEventArgs e)

   at Infragistics.DataManagerBase.<SetDataSource>b__9(DataManagerBase instance, Object s, NotifyCollectionChangedEventArgs e)

   at Infragistics.WeakEventHandler`3.OnEvent(Object source, TEventArgs eventArgs)

   at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)

 It seems, that the latest 2016.2 version has the fix.

Regards

Jarek

Hello Pranav,

I can confirm that the NullReferenceException when a node is removed is fixed and is not reproducible in versions ‘15.2.20152.2212’, ‘16.1.20161.2174’ and ‘16.2.20162.2045’.

Please let me know if you have any other questions.

Please ignore previous post. I misread the version in your post. I was testing with version ‘16.1.20161.2056’ and the issue has been resolved for versions ‘15.2.20152.2212’, ‘16.1.20161.2174’ and ‘16.2.20162.2045’. Please confirm if this is correct. I have yet to test with versions that you have stated.

Hi,

I used your example with following version '16.1.20161.2056'. I still get the error of null exception. As per your previous post this version should have it resolved, but doesn't seem like it has been resolved for this version. Can you please confirm once again if this version has the issue resolved.

Hello,

The fix for issue 221815 was released and is available for versions 15.2.20152.2212, 16.1.20161.2174 and 16.2.20162.2045.

I have verified using those versions and the attached sample project that no NullReferenceException is thrown. Please run the sample and let me know if the behavior is different on your side. If the project does not illustrate your scenario correctly, do not hesitate to modify it and upload it back so I can investigate the behavior further.

Do not hesitate to ask if you have any questions.