You can make any C1RadialMenuItem checkable by setting its IsCheckable property to True.
In the C1RadialMenu, a checked item is marked similarly to a highlighted item instead of with a typical check mark. You can see the Insert Above option checked in the following image.
Note that the check is thinner than the highlight you can see in the RadialMenu Elements topic:
To create a checkable C1RadialMenuItem as in the previous image, follow these steps:
Once you run the project, open the C1RadialMenu. To add a check mark, click the C1RadialMenuItem.