Repro actions:
1) Hit the "End" key to go to the bottom
2) Hit the "Home" key to go back to the top
3) Mouse wheel does not move the scroll
4) The scroll arrows don't work either
5) They keyboard arrows don't work either, the selected item is displayed but they scroll bar does not move

See this video for reference.

Currently when the UI Virtualization is enabled, the RadTreeView sets the IsExpanded property of the RadTreeViewItems to False when they don't have any children. We can add a mechanism by which this can be stopped. 

When IsVirtulizing is set to true and there are many items in the tree view pressing several times PageUp key brings the view port to the beginning of the tree rather to the previous page.

The TreeViewItems are expanded and collapsed on MouseLeftButtonUp which leads to an expand/collapse operation even if the MouseLeftButtonDown event was fired by another element. This can be easility reproduced if you hold down the mouse left button over any element outside the RadTreeView and then releasing it over any RadTreeViewItem when the RadTreeView IsExpandOnSingleClickEnabled is True.

It can also be reprorduced with the following steps:
1) left click on a node and hold the mouse button down
2) release the mouse when over a non-selected node that has children.
The result is expanding/collapsing the unselected node.

SelectedItems collection does not work correctly when the RadTreeView is virtualized and ContainerBindings (SL) / Style Bindings (WPF) are used for binding the IsSelected property.


The issue is not reproducible with R3 2016 version of RadTreeView with both Multiple and Extended Selection mode.
Please open a new support thread with detals from your scenario if you encounter similar issue.

Tree is Virtualized and bind to colelction of DataItems.
On a button click, we add new Dataitem with IsInEditMode = true (bound to IsInEditMode of the RadTreeViewItem).
The new Item is in edit mode but the textBox in the ItemEditTemplate has no DataContext so no actual editing  can be performed.

Scenario casn be solved with adding the item, then switch its editmode in dispatcher:
DataItem item = new DataItem() { Name = "Item Editable" };
             
            (this.tree.ItemsSource as ObservableCollection<DataItem>).Insert(0, item);

            Dispatcher.BeginInvoke(new Action(() =>
            {
                item.IsInEditMode = true;
            }), DispatcherPriority.Loaded);

The XAML team has recently reviewed this issue and will not be addressing it as at this time the team is focusing on the bugs impacting the highest number of developers. If you have encountered this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item.

RadTreeView and RadTreeViewItem ExpandAll() method sets the IsExpanded property to True to all items even if an Item has no children to display. This causes an issue when using the DefaultImageSrc and ExpandedImageSrc properties as the last-level items will be displayed with an ExpandedImageSrc as their IsExpanded property it set to True. However, as these items have no children, they should use the DefaultImageSrc.

Root level items ItemTemplate is incorrectly set after virtualization when using HierarchicalDataTemplate with ItemTemplateSelector.
This causes the second level items to use incorrect data template.

Items are lost after reexpanding when TreeView is Virutalized and items are set in XAML.
Currently the TreeView does not support virtualization when using XAML items.

Reason for Decline: Virtualization is not supported in non-databound treeviews.

When a checked item is loading on demand its check state is lost.
This issue is applicable for both WPF and Silverlight.
And the issue is present always (no matter if the RadTreeView is databound, virtualized, etc).

Edit: Please use the approach from this help article if you need checkboxes in the RadTreeView.
http://docs.telerik.com/devtools/wpf/controls/radtreeview/how-to/howto-tri-state-mvvm.html

The XAML team has recently reviewed this issue and will not be addressing it as at this time the team is focusing on the bugs impacting the highest number of developers. If you have encountered this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item.

Setting a non-default value to the RadTreeView ItemsIndent property disarranges the lines

TreeView: When the header of an Item is set to a TextBox, the selection of a RadTreeViewItem is incorrect

The original reported issue is that the following style does not work as expected.
<Style TargetType="telerik:RadTreeViewItem">
<Style.Triggers>
<Trigger Property="IsKeyboardFocusWithin" Value="True">
<Setter Property="IsSelected" Value="True" />
<Setter Property="Tag" Value="Selected" />
</Trigger>
<Trigger Property="IsKeyboardFocusWithin" Value="False">
<Setter Property="IsSelected" Value="False" />
<Setter Property="Tag" Value="Unselected" />
</Trigger>
</Style.Triggers>
</Style>

This is not supported by the RadTreeView Selection logic. Once the trigger applies with Selected / True, the IsSelected property is Locally set via the selector's code. This means future work of the trigger will not be successful over the IsSelected Property.
==================
The XAML team has recently reviewed this issue and will not be addressing it as at this time the team is focusing on the bugs impacting the highest number of developers. If you have encountered this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item.

Currently, in Extended SelectionMode,  RadTreeView selects multiple Items with Shift + Click selection only if there is another RadTreeViewItem already selected with mouse.

Other controls like RadListBox, RadGridView hold reference to the business object which should be the start (the target) of the multiselection. RadTreeView holds such reference with weak reference to the container (RadTreeViewItem) and only if this container is selected with Mouse.

Adding such method (SetSelectionAnchor) in RadTreeView will help users better control the multiselection process.

Change the SelectedValue implementation to allow a TwoWay binding

When a large number of items are selected through extended selection (with a lot of items on the first level of the RadTreeView) the selection does not work correctly. 

BindingExpressionError occurs in situations  when the tree is virtualized and TemplateSelectors are used

When TreeView is databound to RadObservableCollection and Suspen/Resume Notifications are used when removing items the Selected items collection contains empty object at the end after deleting item and selecting another one.

As a workaround you can use ObservableCollection.


The XAML team has recently reviewed this issue and will not be addressing it as at this time the team is focusing on the bugs impacting the highest number of developers. If you have encountered this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item.

Ability to have both static and bound RadTreeViewItems or different hierarchy levels.

Reason for decline: There is no proper way this to be implemented.
 This would require huge refactoring of the DragDrop, Styling, Editing, Virtualization logic. 
Complexity of such task  is close to writing a new control from scratch.

The built-in drag drop mechanism works with the containers of the items and makes a snapshot of them for the DragVisual. Thus, dragging multiple selected items that are not present in the viewport is not possible.

The children count is read incorrectly by MS Narrator