How to refresh listbox after item deleted from listbox

I have a drop down listbox. Nex to the listbox is a delete button where people can delete the selected item.
Once the delete button is pressed, I need to reset the listbox to it's default value "--Select--"
I the need to refresh the listbox so that it does not contain the item that was selected and deleted.
How do I do this? I tried rebinding the data source and listbox but that didn't work. This is what I tried:
            dsGroupNames.DataBind();
            ddlGroupNames.DataBind();
...