PrincipalPermission.Union(System.Security.IPermission) creates a permission representing the criteria of a given set of individual System.Security.Permissions.PrincipalPermission objects. It is useful for compactly representing a set of conditions to test. For example, with the declarations
code reference: System.Security.Permissions.PrincipalPermission#3
(ppBob.Union(ppLouise)).Demand() will succeed if the current principal represents Bob in the role of Administrator or Louise in the role of Administrator.