The ComboBox class provides an extension point in ArcGIS Explorer. A class which inherits from the ComboBox class can be shown as a visual list which is displayed on the Ribbon, providing an opportunity to run code when the user selects an item from the ComboBox. Other extension points are Button, DockWindow, Gallery, CheckBox and Extension.

The simplest way to create a new ComboBox is to use the templates provided in the Visual Studio Tools for ArcGIS Explorer. For step by step instructions on creating a new ComboBox using these templates, see the Creating a custom ComboBox walkthrough.

In the constructor of the ComboBox, add ComboItem objects to the Items property - these items will be displayed in the ComboBox. Override the OnSelectionChange(ComboItem) method to run code when the user selects an item from the list displayed by the ComboBox. Optionally, override the OnUpdate()()() method to periodically run code; note that the OnUpdate method should only perform brief operations to maintain responsiveness of the application.

Note:
A ComboBox must be included in an add-in project and described in the AddIns.xml file which is part of that project in order to be loaded by ArcGIS Explorer. These steps are automated if the ComboBox is created by using the Visual Studio Tools for ArcGIS Explorer templates.