In order to display items, you have to populate the RadMenu control with some data. You can do this in two ways:
Manually, by adding items to the Items collection.
With data binding, by using the ItemsSource property.
You can't have items added manually to the Items collection and set the ItemsSource at the same time.
In this section you will find:
Data Binding Support Overview - here you will find information about the supported data sources and RadMenu's data binding basics.
Populating RadMenu Using Static Items - explains how to populate your RadMenu control with some static data in XAML.
Populating RadMenu with Dynamic Data - explains how to bind the RadMenu to a collection that holds the information about its items.
Template and Style Selectors - explains the properties exposed for usage with the template and styles selectors.