Just wanted to confirm that this also solved my issue, so thank you for posting this. Took me a while to figure this out.
I believe this is only an issue when you are using implicit styles
. In my case, when I switched the Telerik.Windows.Controls.Navigation assembly (which contains the RadTreeView) to the NoXaml version used for implicit styling, this issue came up. When I switched back to the all-including Xaml version, the issue disappeared. However, this is typically not what you want, if you have decided to use implicit styles. So we really need to get to the root of this issue.
Here's my attempt at an explanation: In the documentation
, including the BasedOn property is the approach explained. Using BasedOn is what you need to do in order to "override" a style that has already been defined by the Telerik team, and included in the Theme Xaml DLL you're using.
In the case above, you want to modify the RadTreeViewItem style by just setting the properties you want to override. In order to do that, you must include the BasedOn property, otherwise you would have to include all
properties of the RadTreeViewItem.
In my case, I wanted to bind the IsExpanded property of each node in the tree to the matching property of my view model for the tree, and including the BasedOn property also did the trick here.