PrimaryGroup sets or gets the group of the SD. If the property OwnPrimaryGroup is true and the property is set, the old Owner TJwSecurityId instance will be freed and the new owner will be copied into a new instance. So there will be two instances of this SID and the original instance is not touched and must be freed if necessary. If the property OwnPrimaryGroup is false, the old Owner TJwSecurityId will not be freed and the new one will directly point to the new SID. 

See Owner for information about how to use this property.

TJwSecurityDescriptor Properties