Telerik RadComboBox has a rich design-time support, allowing you to add/remove/edit items and see the changes reflected immediately.
To build a combobox:
- Drag an instance of Telerik RadComboBox from the toolbox onto the webform.
- Right-click the instance, and from the context menu, select the Build RadComboBox command.

This will pop up RadComboBox Collection Editor, shown below.

The RadComboBox Collection Editor is divided into two panes. The members on the left outline the current structure of the combobox. The property grid on the right displays the properties of the currently selected item.
The Add button adds a new item. The Remove button removes the selected item.
Click OK to save your changes; click Cancel to discard them.
See Also