Dev2.FileIO.CheckPermissions C# (CSharp) Method

        public static bool CheckPermissions(WindowsIdentity user, string path, FileSystemRights expectedRights)
        {
            var fi = new FileInfo(path);
            var di = new DirectoryInfo(path);
            AuthorizationRuleCollection acl;

            if (fi.Exists)
            {
                acl = fi.GetAccessControl().GetAccessRules(true, true, typeof (SecurityIdentifier));
            }
            else if (di.Exists)
            {
                acl = di.GetAccessControl().GetAccessRules(true, true, typeof (SecurityIdentifier));
            }
            else
            {
                return false;
            }

            // gets rules that concern the user and his groups
            IEnumerable<AuthorizationRule> userRules = from AuthorizationRule rule in acl
                where user.Groups != null && user.User != null && (user.User.Equals(rule.IdentityReference)
                                                                   || user.Groups.Contains(rule.IdentityReference))
                select rule;

            FileSystemRights denyRights = 0;
            FileSystemRights allowRights = 0;

            // iterates on rules to compute denyRights and allowRights
            foreach (FileSystemAccessRule rule in userRules)
            {
                if (rule.AccessControlType.Equals(AccessControlType.Deny))
                {
                    denyRights = denyRights | rule.FileSystemRights;
                }
                else if (rule.AccessControlType.Equals(AccessControlType.Allow))
                {
                    allowRights = allowRights | rule.FileSystemRights;
                }
            }

            allowRights = allowRights & ~denyRights;

            // are rights sufficient?
            return (allowRights & expectedRights) == expectedRights;
        }