Set Header to true to specify that an item in the check listbox acts as a header rather than a selectable item. By setting Header to true for various items in the list, you can divide the check listbox into multiple sections, where each header labels the beginning of a section. 

When Header is true for an item, the list box does not display a check box next to the item, but rather, it displays only the item's text. This item is drawn with a background color of HeaderBackgroundColor and a font color of HeaderColor, which can be used to make it visually distinct from the checkable items in the list box. 

Index is the index of the item. 

HeaderColor 

HeaderBackgroundColor