Using a custom style you can bind the RadPanelBar IsEnabled property to a property from your model. This way you can control which panel bar item to be enabled or not.
As for your other question, you can use two options using a Triggers or edit the default Template of the control which depends on the theme wich you are using so you can change the appearance of the disabled items.
I'll explain why below. Our latest themes -- Green and Office2016 are supported in WPF only and thus the changing of visual appearance is made with Triggers primarily (supported in WPF only). So for these themes using a Trigger that changes the Background (for example) color on an IsEnabled property is absolutely correct approach and should work without problems.
On the other side, our older themes (before Green) are supported in both SL and WPF platforms. This is the reason why we've been using the Visual States instead of Triggers for them. Please mind that even though combining both VisualStates and Triggers in a Control Template is absolutely possible this might confuse you in this case and might lead to unexpected results. For example, when you are triggering IsEnabled = False this is practically equal to executing a Disabled Visual State. You are trying to change the Background (for example
) of the RadPabelBarItem but the Disabled VisualState (that is already present in the theme style you are using) adds additional Border visual on top and changes its Background.
You have two options to choose from in such case:
1. You might either modify the ControlTemplate of the RadPanelBarItem that we ship with the current theme and comment or delete the Disabled VisualState so that it don't interfere with your Trigger. You can take a look at the Editing Control Templates
help article in our documentation.
2. Directly modify the Disabled VisualState in the ControlTemplate and don't mix triggers with visual states that are executing the same action.
Telerik by Progress
Telerik UI for WPF is ready for Visual Studio 2017 RC! Learn more.