Source Code & Description
RadComboBox fully supports templates. You can embed any content inside a RadComboBox template, including
HTML markup and ASP.NET server controls, as well as other third party controls (and actually any control from
the Telerik RadControls suite as well).
The syntax is very similar to what you're used to from the default DataGrid control. If you do not specify an ItemTemplate,
all RadComboBox items are rendered using their Text property as plain text. If you specify <ItemTemplate>, then
the respective template is used for rendering.