public override NSObject ObjectValueForItem (NSComboBox comboBox, int index)
{
if (cbox == null)
return null;
if (string.IsNullOrEmpty (cbox.DisplayMember))
returnString = new NSString (cbox.Items[index].ToString ());
else
returnString = new NSString (Util.GetPropertyStringValue (cbox.Items[index], cbox.DisplayMember));
return returnString;
}