Get share folder effective rights using C#

 class NetDirectorySecurity : NativeObjectSecurity
    {
        public NetDirectorySecurity(string ResName, AccessControlSections IncludeSections)
            : base(true, ResourceType.LMShare, ResName, IncludeSections)
        {
        }

        private static FileSystemRights RightsFromAccessMask(int accessMask)
        {
            return (FileSystemRights)accessMask;
        }

        public sealed override AccessRule AccessRuleFactory(IdentityReference identityReference, int accessMask,
            bool isInherited, InheritanceFlags inheritanceFlags, PropagationFlags propagationFlags, AccessControlType type)
        {
            return new FileSystemAccessRule(identityReference, RightsFromAccessMask(accessMask), inheritanceFlags, propagationFlags, type);
        }

        public sealed override AuditRule AuditRuleFactory(IdentityReference identityReference, int accessMask,
            bool isInherited, InheritanceFlags inheritanceFlags, PropagationFlags propagationFlags, AuditFlags flags)
        {
            return new FileSystemAuditRule(identityReference, RightsFromAccessMask(accessMask), inheritanceFlags, propagationFlags, flags);
        }

        public override Type AccessRightType { get { return typeof(FileSystemRights); } }
        public override Type AccessRuleType { get { return typeof(FileSystemAccessRule); } }
        public override Type AuditRuleType { get { return typeof(FileSystemAuditRule); } }
    } 


                        NetDirectorySecurity nds = new NetDirectorySecurity(sharedName, AccessControlSections.Access);
                     
                        var permissions = nds.GetAccessRules(true, true, typeof(SecurityIdentifier));
                        FileSystemRights denyRights = 0;
                        FileSystemRights allowRights = 0;

                        var accessRules = permissions.Cast<FileSystemAccessRule>().Where(ar => ar.IdentityReference.Value == sid).ToList();

                        if (accessRules.Count == 0) mask = 0;

                        foreach (var accessRule in accessRules)
                        {
                            if (accessRule.AccessControlType == AccessControlType.Deny)
                            {
                                denyRights |= accessRule.FileSystemRights;
                            }
                            else
                            {
                                allowRights |= accessRule.FileSystemRights;
                            }
                        }

                        var mask = (int)((allowRights | denyRights) ^ denyRights);