Get nETBIOSName from a UserPrincipal object

Question

I am using the System.DirectoryServices.AccountManagement part of the .Net library to interface into ActiveDirectory.

Having called GetMembers() on a GroupPrincipal

Answer 1

You have two choices that I can think of.

1. Parse, or take everything that is on, the right of name@fully.qualified.domain.name;
2. Use the System.DirectoryServices namespace.

I don't know about UserPrincipal, neither do I about GroupPrincipal. On the other hand, I know of a working way to achive to what you want.

[TestCase("LDAP://fully.qualified.domain.name", "TestUser1")] 
public void GetNetBiosName(string ldapUrl, string login)
    string netBiosName = null;
    string foundLogin = null;

    using (DirectoryEntry root = new DirectoryEntry(ldapUrl))
        Using (DirectorySearcher searcher = new DirectorySearcher(root) {
            searcher.SearchScope = SearchScope.Subtree;
            searcher.PropertiesToLoad.Add("sAMAccountName");
            searcher.Filter = string.Format("(&(objectClass=user)(sAMAccountName={0}))", login);

            SearchResult result = null;

            try {
                result = searcher.FindOne();

                if (result == null) 
                    if (string.Equals(login, result.GetDirectoryEntry().Properties("sAMAccountName").Value)) 
                        foundLogin = result.GetDirectoryEntry().Properties("sAMAccountName").Value
            } finally {
                searcher.Dispose();
                root.Dispose();
                if (result != null) result = null;
            }
        }

    if (!string.IsNullOrEmpty(foundLogin)) 
        using (DirectoryEntry root = new DirectoryEntry(ldapUrl.Insert(7, "CN=Partitions,CN=Configuration,DC=").Replace(".", ",DC=")) 
            Using DirectorySearcher searcher = new DirectorySearcher(root)
                searcher.Filter = "nETBIOSName=*";
                searcher.PropertiesToLoad.Add("cn");

                SearchResultCollection results = null;

                try {
                    results = searcher.FindAll();

                    if (results != null && results.Count > 0 && results[0] != null) {
                        ResultPropertyValueCollection values = results[0].Properties("cn");
                        netBiosName = rpvc[0].ToString();
                } finally {
                    searcher.Dispose();
                    root.Dispose();

                    if (results != null) {
                        results.Dispose();
                        results = null;
                    }
                }
            }

    Assert.AreEqual("INTRA\TESTUSER1", string.Concat(netBiosName, "\", foundLogin).ToUpperInvariant())
}

Other related information or links available in this SO question.
C# Active Directory: Get domain name of user?
How to find the NetBIOS name of a domain