How to do logout functionality in C# smart device application?

I am developng Smart device application in C#. It is a window application. In this application I am using Login form to authenticate the users. Only authenticated users can login into the system. In this application I am calling java web services which resides on another machine. I am passing mobile number & pas开发者_C百科sword from mu application's login form to the java web services. The java web services returns the userid after successful authentication. I made this userid static so that it can be used frequently with other web services. I using statc variables in this application so that they can be used at application level. After deploying the application I can see that emulator provides the close button with multiplicaton symbol. In this way I can close my form as well as application. But I want to provde one logout link in my application. Can I provide logout functionality in C# window application ? If yes, how to do that ? Please make sure that all the functions of .net framework does not work with .net compact framwork? Can you provide me the code or link through which can resolve the above issue ?

Why don't you "reset" required variables (if there are any that need to) and display the Login form again ?