System.Security 2.0.0.0 4.0.0.0 System.Enum This flag represents either a single or multiple certificate selection using the method. Specifies the type of selection requested using the method. Field 2.0.0.0 4.0.0.0 System.Security.Cryptography.X509Certificates.X509SelectionFlag A multiple selection. The user can use the SHIFT or CRTL keys to select more than one X.509 certificate. Field 2.0.0.0 4.0.0.0 System.Security.Cryptography.X509Certificates.X509SelectionFlag A single selection. The UI allows the user to select one X.509 certificate.