.Net combobox allow typing the value not just in the list -

in .net form, want have combobox allows customer choose value dropdown list , can type value not in dropdown list. set dropdownstyle = comboboxstyle.dropdown. property allows type value in list. otherwise got error: formatting, display. setting property dropdownstyle = comboboxstyle.simple not working because display dropdown list. if inherit combobox datagridviewcomboboxcell, not display dropdown list. if let program dynamically add new item when customer type new value, dropdown list become bigger , bigger, it's not want. so, there way let combobox allow typing value not in list , keep dropdown list not change? lot