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?