I have a WebDropDown populated at the server, and would like to client-side set or clear the checkbox on a particular item

<ig:WebDropDown ID="MyDropDownControl" runat="server" DisplayMode="DropDownList" EnableMultipleSelection="True" MultipleSelectionType="Checkbox" />

var ctrl = $find('MyDropDownControl');

var item0 = ctrl.get_items().getItem(0);

// these next two statements do select/unselect

// but no effect to the checkbox

item0.select();

item0.unselect();

// this does set the checkbox, but seems rather dangerous

item0.get_element().childNodes[0].checked = true;

Thank you!