Hi Peter Zhao,
Please first excuse me for misleading you with a WPF solution instead of SL`s one.
In Silverlight , you can inherit RadTreeView and RadTreeViewItem and override their OnKeyDown and OnKeyUp protected methods like so:
public class CustomTreeView :RadTreeView
protected override void OnKeyDown(KeyEventArgs e)
protected override void OnKeyUp(KeyEventArgs e)
The key thing here is that you don't make call to base.OnkeyDown(e); and base.OnkeyUp(e).
The described approach is realized in the attachment. So please give it a try and let us know if it helps you.
the Telerik team
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