Search if user is part of specific group

Question

We have implemented a functionality via the Core Service and we want to have this functionality only available to one SDL Tridion group (e.g. TridionGrp) and all others should get an unauthorized error.

We are able to check for the users who are directly part of this TridionGrp however how can we check if a user part of another group (e.g. TridAccess) while that other group is part of TridionGrp.

So how can we recursively check the user membership in order to validate the access?

Answer 1

Update

If Peter is correct, my answer makes no sense of course! I will leave it for now until Hiren has confirmed that the group memberships are indeed expanded automatically.

Original answer

As far as I know, the only way to do this is to go through the group memberships recursively. For example (untested code!!)

TrusteeData trustee = (TrusteeData) client.Read(TrusteeID, new ReadOptions());
List<GroupMembershipData> groupMemberships = GetGroupMemberships (trustee);

private List<GroupMembershipData> GetGroupMemberships (TrusteeData trustee) 
{
    List<GroupMembershipData> memberships = new List<GroupMembershipData>();
    foreach (GroupMembershipData groupMshpData in trustee.GroupMemberships)
    {
        memberships.Add(groupMshpData.Group);
        subMemberships = GetGroupMemberships(groupMshpData.Group);
        if (subMemberships.Count > 0)
            memberships.AddRange(subMemberships);
    }
    return memberships;
}

Answer 2

Group memberships are automatically expanded for the current user.

So just call GetCurrentUser() and check if the relevant group is in the GroupMemberships array.