How can I modify the AJAX Cascading Dropdownlist to use a Listbox as the last control

Hello - I have a need to modify the AJAX Cascading Dropdownlist where the last control is a listbox.

Just changing the last control to a listbox won't do it since I get the following error:

Unable to cast object of type 'System.Web.UI.WebControls.ListBox' to type 'System.Web.UI.WebControls.DropDownList'

To me it looks like the CascadingDropdownExtender.cs file would need to be modified but I am not sure where to start

The problem is that the targetcontrol on the extender is set to DropDownList instead ListControl which is more inclusive. You couldopen a work item for this and we will look into fixing this.