Show all domains that your computer belongs to:

public static void ShowMyDomains()
{
    DomainCollection domains = Forest.GetCurrentForest().Domains;



foreach (Domain domain in domains)
{
    Console.WriteLine(domain.Name);
}




}

Show all users in the domain:

public static void ShowDomainUsers()
{
    DirectoryEntry domain = new DirectoryEntry("LDAP://domain.com/CN=Users,DC=Domain,DC=com");



foreach (DirectoryEntry child in domain.Children)
{
    Console.WriteLine(child.Name);
}




}

Show all computers in the domain:

public static void ShowDomainComputers()
{
    DirectoryEntry domain = new DirectoryEntry("LDAP://domain.com/CN=Computers,DC=Domain,DC=com");



foreach (DirectoryEntry child in domain.Children)
{
    Console.WriteLine(child.Name);
}




}

Resources

  1. LDAP on Wikipedia. It read like Latin.

  2. How to do almost everything in Active Directory via C# from the ever-excellent Code Project. Reads like Pig-Latin.

  3. Active Directory Authentication from ASP.NET from MSDN.