Hi Richard Slade,
Thank you for contacting us. As far as I understand the issue is about the visual part of the selection in RadListBox. In order to remove the selection border that appears you should customize the theme that you are using. Here is a step by step tutorial:
1. Select the RadListBox, click on the Smart Tag and select Open Theme Builder
2. Now click on one of the items, so that the item border is painted in red. You can also navigate the TreeView that appears on the left of the screen using the following path: RootRadElement-> RadListBoxElement-> RadScrollBarLayoutPanel-> RadVirtualizesStackViewport-> RadListBoxItem-> BorderPrimitive
3. Delete all the states of the BorderPrimitive by removing the tabs that appear in the bottom part of Visual Style Builder. Further, Save your theme (Please, note that the name of the theme that appears in the upper right corner should be the same as the name of the theme you want to use in your application)
4. Now you can apply your custom theme to the RadListBox via RadThemeManager
For your convenience, I have already customized the ControlDefault theme. If you encounter any difficulties customizing your own theme, please, let me know which theme you are using. I will be glad to customize it for you.
the Telerik team