A ComboBox is a combination of a single-line text box with drop-down list. The ComboBox item in this is highlighted below:
The ComboBox can be added at design-time using the Floating Toolbar or Collection Editor. Refer this topic for detailed information.
A ComboBox can also be added to the C1Ribbon control through the code using the RibbonComboBox class. This is depicted in the code below: