public bool IsMemberOfGroup(string groupName) { if (groupName == null) { throw new ArgumentNullException(nameof(groupName)); } var userSearchResult = directory.TryGetPrincipal(PrincipalSearchType.Users, this.userId.ToFullyQualifiedName()); if (userSearchResult == null) { return(false); } var groupSet = LDAP.ExtractGroupNames(userSearchResult); return(groupSet.Contains(GroupId.Parse(groupName)?.Principal ?? groupName)); }