By design in Windows8, Office2013 and Windows8Touch themes, there is no border in the ReadOnly VisualState of the RadMaskedInputControls. You have several options:
- Edit the default ControlTemplate of the RadMaskedInputBase and control what is changing in ReadOnly VisualState
- You can consider using IsEnabled = False instead of IsReadOnly = True.
- You can add Border on top of the MaskedInput in your application. the bind the Visibility of the border to the IsReadOnly property of the MaskedInput via telerik's BooleanToVisibilityConverter
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