This sample demonstrates the cascading functionalities of the ComboBox. Choose a country from countries ComboBox, then respective states will be loaded in the second ComboBox and the same has to done between states and cities ComboBox.
The Cascading ComboBox is the series of ComboBox, where the value of one ComboBox depends on the another ComboBox value. This can be configured by using the change event of parent ComboBox. Within that change event handler, you should load the data to child ComboBox based on the selected value of parent ComboBox. More information on the Cascading feature configuration can be found in the documentation section.