C# Active Directory: Get domain name of user?

Question

I know that this type of question has been asked before, but other methods are failing me right now.

As it stands our windows service polls AD, given an LDAP (i.e. L

Answer 1

Since I could not find any example code I would like to share my own solution. This will search the parents of the DirectoryEntry object until it hits the domainDNS class.

using System.DirectoryServices;

public static class Methods
{
    public static T ldap_get_value(PropertyValueCollection property)
    {
        object value = null;
        foreach (object tmpValue in property) value = tmpValue;
        return (T)value;
    }

    public static string ldap_get_domainname(DirectoryEntry entry)
    {
        if (entry == null || entry.Parent == null) return null;
        using (DirectoryEntry parent = entry.Parent)
        {
            if (ldap_get_value(parent.Properties["objectClass"]) == "domainDNS") 
                return ldap_get_value(parent.Properties["dc"]);
            else 
                return ldap_get_domainname(parent);
        }
    }
}

Use it like this:

string[] _properties = new string[] { "objectClass", "distinguishedName", "samAccountName", "userPrincipalName", "displayName", "mail", "title", "company", "thumbnailPhoto", "useraccountcontrol" };
string account = "my-user-name";
// OR even better:
// string account = "my-user-name@DOMAIN.local";

using (DirectoryEntry ldap = new DirectoryEntry())
{
    using (DirectorySearcher searcher = new DirectorySearcher(ldap))
    {
        searcher.PropertiesToLoad.AddRange(_properties);
        if (account.Contains('@')) searcher.Filter = "(userPrincipalName=" + account + ")";
        else searcher.Filter = "(samAccountName=" + account + ")";
        var user = searcher.FindOne().GetDirectoryEntry();

        Console.WriteLine("Name: " + Methods.ldap_get_value(user.Properties["displayName"]));
        Console.WriteLine("Domain: " + Methods.ldap_get_domainname(user));
        Console.WriteLine("Login: " + Methods.ldap_get_domainname(user) + "\\" + Methods.ldap_get_value(user.Properties["samAccountName"]));
    }
}

I haven't got a forest to test it on but in theory this should cut it.