Elevated Trust is a new feature in Silverlight 4 which allows Silverlight apps to be run with fewer security restrictions. To check whether an app is running in elevated trust use the HasElevatedPermissions property.
If an app requires elevated trust, users must first consent before installing the application for out-of-browser use. Thus you will not normally have to detect whether an app is running in elevated trust. Instead, you can simply check if an app is running outside of the browser by checking the Application.IsRunningOutOfBrowser property.