In addition to the full-featured C1DropDown control, DropDown for WPF includes parts of the C1DropDown control, C1DropDownButton and C1SplitButton that allow you to further customize your application.
C1DropDown is similar to a traditional drop-down control allowing you to choose from a selection of items, C1DropDownButton works like a drop-down control but looks like a button, C1SplitButton has two parts: the header and the arrow which you can customize so that clicking in the arrow will open the drop-down list, and pressing in the header button will typically apply the current selection.