Your Privacy Matters: We use our own and third-party cookies to improve your experience on our website. By continuing to use the website we understand that you accept their use. Cookie Policy
220
Issue on child Item Removal when Parent is Collapsed - XamdataTree
posted

I am using Infragistics V16.1 . I am giving snipped of code where the issue occurs 

Here ParentColl is ObservableCollection of TreeElement which has children of Type TreeElement bind to XamDataTree.

Xaml:

<ig:XamDataTree x:Name="MyTree" Grid.Row="0" 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>

On the click of a button I am trying to remove the childitem when parent is collapsed . Here is sample 

        TreeElement ChildItem = Parent.Children.FirstOrDefault();

          Parent.Children.Remove(ChildItem);

The  System.NullReferenceException  is thrown only when Parent is collapsed. Help me find a solution. 

Exception Thrown is 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.ObjectModel.ObservableCollection`1.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
at System.Collections.ObjectModel.ObservableCollection`1.RemoveItem(Int32 index)
at System.Collections.ObjectModel.Collection`1.Remove(T item)






Parents
No Data
Reply
  • 17475
    Offline posted

    Hello Vetriselvan,

    XamDataTree nodes are virtualized to improve the performance when the control has a large amount of items. When you try to access a child element of a node which is not expanded, this child element is not rendered because it is not in view and that will cause a NullReferenceException.

    To access the UI element which is not in view you can turn off the virtualization by placing the XamDataGrid in a container which measures its children with infinite height e.g. StackPanel or ScrollViewer.

    Another approach would be to operate with the data source of the XamDataTree and remove the element from there so it is no longer displayed as a node.

    Please feel free to let me know if you have any questions.

Children