Editable dropdownlist

Question

I need the dropdownlist in the web application to be editable,
the DDL should be similar to combobox of windows application.
The dropdownlist should be in such a way that the user should be able to enter new value
that is not present in the ddl.is there any way i can do it?

is it possible to use System.windows.forms and inherit the combobox in web application?
I have tried all means but i need to do this in web application using c# dotnet 3.5.