Using ASP.NET membership providers on a client in a WinForms application is insecure, since a malicious user can replace the provider by one of his own choosing simply by editing the application configuration file.
What exactly are you trying to achieve, and is security important?
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…