ASPxHtmlEditor - How to implement cascade ToolbarComboBoxes bound to data sources

This example demonstrates how to implement cascading ToolbarComboBoxes on the ASPxHtmlEditor toolbox.
To provide this functionality, the ASPxHtmlEditor was placed into the ASPxCallbackPanel.
The selected value of the main combo box is transmitted as a parameter in a callback to the ASPxCallbackPanel. Then this value is used as a select parameter for the data source of the second combo box.