Bind To Row's Expanded State

[Terry Foster]

I need my view model to know, as a parent item, if it's row is expanded or collapsed and, ideally, be able to likewise expand or collapse it's row (without interacting directly with the TreeListView).  Is there a way to do this?

Thanks,
Terry

[Yavor Georgiev]

Hi Terry Foster,

 You need to handle the RowLoaded event like so:

var row = e.Row as TreeListViewRow;

if (row != null)
{
  var binding = new Binding("IsExpanded") { Source = row.Item };
  binding.Mode = BindingMode.TwoWay;
  row.SetBinding(TreeListViewRow.IsExpandedProperty, binding);
}

This will bind the row's expanded state to the IsExpanded property of your data item.

Sincerely yours,
Yavor Georgiev
the Telerik team

[Peter]

Hi,

I have used you code but getting run-time error:

Error HRESULT E_FAIL has been returned from a call to a COM component.

StackTrace:

   v MS.Internal.XcpImports.CheckHResult(UInt32 hr)
   v MS.Internal.XcpImports.Collection_Clear[T](PresentationFrameworkCollection`1 collection)
   v System.Windows.PresentationFrameworkCollection`1.ClearImpl()
   v System.Windows.PresentationFrameworkCollection`1.Clear()
   v Telerik.Windows.Controls.GridView.GridViewBaseVirtualizingPanel.OnItemsChangedInternal(Object sender, ItemsChangedEventArgs args)
   v Telerik.Windows.Controls.GridView.GridViewBaseVirtualizingPanel.OnItemsChangedHandler(Object sender, ItemsChangedEventArgs args)
   v Telerik.Windows.Controls.GridView.GridViewItemContainerGenerator.OnRefresh()
   v Telerik.Windows.Controls.GridView.GridViewItemContainerGenerator.Refresh()
   v Telerik.Windows.Controls.GridView.GridViewDataControl.OnItemsChanged(NotifyCollectionChangedEventArgs e)
   v Telerik.Windows.Controls.GridView.BaseItemsControl.OnItemCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   v System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   v Telerik.Windows.Data.DataItemCollection.OnCollectionChanged(NotifyCollectionChangedEventArgs e)
   v Telerik.Windows.Data.DataItemCollection.OnCollectionViewCollectionChanged(Object sender, NotifyCollectionChangedEventArgs e)
   v Telerik.Windows.Data.Listener`2.ReceiveWeakEvent(Object sender, TArgs args)
   v Telerik.Windows.Data.WeakEvent.WeakListener`1.Handler(Object sender, TArgs args)
   v System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
   v Telerik.Windows.Data.QueryableCollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
   v Telerik.Windows.Data.HierarchicalCollectionView.RefreshOnExpandCollapse(IHierarchicalChildCollectionView expandedView)
   v Telerik.Windows.Data.HierarchicalCollectionView.ExpandItem(Object item)
   v Telerik.Windows.Controls.RadTreeListView.ToggleHierarchyItemExpandStateInHierarchyViewFromUI(Object hierarchyItem, Boolean isExpanding)
   v Telerik.Windows.Controls.TreeListView.TreeListViewRow.OnIsExpandedChanged(Boolean oldValue, Boolean newValue)
   v Telerik.Windows.Controls.GridView.GridViewRow.OnIsExpandedChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs e)
   v Telerik.Windows.PropertyMetadata.PropertyChangeHook.OnPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   v System.Windows.DependencyObject.RaisePropertyChangeNotifications(DependencyProperty dp, Object oldValue, Object newValue)
   v System.Windows.DependencyObject.UpdateEffectiveValue(DependencyProperty property, EffectiveValueEntry oldEntry, EffectiveValueEntry& newEntry, ValueOperation operation)
   v System.Windows.DependencyObject.SetValueInternal(DependencyProperty dp, Object value, Boolean allowReadOnlySet, Boolean isBindingInStyleSetter)
   v System.Windows.Data.BindingOperations.SetBinding(DependencyObject target, DependencyProperty dp, BindingBase binding)
   v System.Windows.FrameworkElement.SetBinding(DependencyProperty dp, Binding binding)
   v MyView.ActivityMonitorTreeView_RowLoaded(Object sender, RowLoadedEventArgs e)
   v Telerik.Windows.Controls.GridView.GridViewDataControl.OnRowLoaded(RowLoadedEventArgs e)
   v Telerik.Windows.Controls.GridView.GridViewDataControl.RaiseRowLoaded(GridViewRowItem row)
   v Telerik.Windows.Controls.GridView.GridViewRowItem.MeasureOverride(Size constraint)
   v System.Windows.FrameworkElement.MeasureOverride(IntPtr nativeTarget, Single inWidth, Single inHeight, Single& outWidth, Single& outHeight)

I need rows in RadTreeListView to be expanded according property IsExpanded in my ViewModel. I have tried many approaches to get it work but I am getting just strange results (similar like the above).
Any idea? 
Thanks,

peter

[Nick]

Hello Peter,

The code that is suggested by my colleague is outdated. Unfortunately the current version of the RadTreeListView does not support binding the IsExpanded property. May I ask you to share what is your final goal so I can suggest an alternative? 

Looking forward to hearing from you. 

All the best,
Nik
the Telerik team

[Peter]

Hi Nik,

Thanks for your reply. I will try to describe my situation.
I have RadTreeListView bound to list of ItemViewModel. ItemViewModel represents the viewmodel of entity which is in some state and can have some child entities. ItemViewModel also contains IsExpanded property which is set during initialization as follows:

if (entity.State == States.RUNNING && entity.Childs.Any())
    IsExpanded = true;
else
    IsExpanded = false;

So first time RadTreeListView is loaded I need some rows to be expanded according to their ViewModel IsExpanded property.
I expected to do this by setting binding between rows IsExpanded property and thier appropriated ViewModel IsExpanded property. Unfortunately this straightforward approach doesnt work. Is there some other way how it can be done?
Thanks.

peter

[Nick]

Hi Terry,

The best way to achieve the desired behavior would be to use a style selector for the TreeListView rows, so that they are expanded depending on a property in the business object. You can see examples of RowStyleSelectors here.

Let me know if I can help you further on the matter.

Kind regards,
Nik
the Telerik team

[Mike]

Has there been any updates?  Does the latest TreeListView control support binding IsExpanded property to a property of a custom business object via ContainerBindingsCollection?  Thanks.

[Vlad]

Hi,

 I'm afraid that we still cannot offer such solution. 

Greetings,
Vlad
the Telerik team