title: Clear selected value in UltraOptionSet
body: <p>I have an UltraOptionSet control that is unbound. Once a value has been selected, how can I clear the selected value? I want the net effect of all options in the UltraOptionSet control to be unselected.</p>
  
  <p>I tried setting the Value property to null and DBNull.Value but neither cleared the selected option.</p>