An System.Net.IWebProxy used by every call to instances of System.Net.WebRequest.
WebRequest.GetSystemWebProxy method reads the current user's Internet Explorer (IE) proxy settings. This process includes the IE options to automatically detect proxy settings, use an automatic configuration script, manual proxy server settings, and advanced manual proxy server settings.
If your application is impersonating several users, you can use the WebRequest.GetSystemWebProxy method to retrieve a proxy for each impersonated user.