ASPxComboBox - How to implement cascaded combo boxes when using a large data source

This example demonstrates how to implement cascaded combo boxes scenario when a child ASPxComboBox operates in a Dynamic List Population mode

1) Enable a "child" ASPxComboBox "Dynamic List Population" mode by setting the EnableCallbackMode property to "true"
2) Implement both the ASPxComboBox.OnItemRequestedByValue event and the ASPxComboBox.OnItemsRequestedByFilterCondition events of the "child" ASPxComboBox;
3) Handle the client-side ASPxClientComboBox.SelectedIndexChanged event of the "parent" ASPxComboBox;
4) Perform a custom callback of the "child" ASPxComboBox via the client-side ASPxClientComboBox.PerformCallback method to update the underlying "child" data.