禁用DropDownList某一选项

DisAbleDropDownListItem 

 public void DisAbleDropDownListItem(DropDownList ddl)
        {
            foreach (ListItem li in ddl.Items)
            {
                if (li.Value == "1" || li.Text == "RUN")
                {
                    li.Attributes.Add("disabled", "disabled");
                }
            }
        }