Make a graphic interface in a C# Web Service

Hi all. I made a C# Web Service. I have a client and a server. Server is a .dll. The client interacts with the server (obvious XD). I want to make a graphical interface in the server part that show some information in a window. I´m trying to do it with windows form, but it doens´k work. I cant put a Main in teh server. I added this class to the server: public class FirstForm : Form { public static void Main(){ Application.Run(new FirstForm()); } } but I dont know how can I execute it. How can I show a interface in Server? Thanks!