TreeView items can be created from a hierarchal datasource control such as an XMLDataSource or SiteMapDataSource. This allows you to update the treeview items without having to edit code.
When using multi-level data as ItemsSource for the C1TreeView, you need to specify a C1HierarchicalDataTemplate for the items.
The template will tell the C1TreeView where to find the next level of data, this is done through the "ItemsSource" property of the C1HierarchicalDataTemplate.