c# - Connect to Active Directory via LDAP

Question

I want to connect to our local Active Directory with C#.

I've found this good documentation.

But I really don't get how to connect via LDAP.

Can somebody of you explain how to use the asked parameters?

Sample Code:

  static DirectoryEntry createDirectoryEntry()  
  {  
     // create and return new LDAP connection with desired settings  

     DirectoryEntry ldapConnection     = new DirectoryEntry("rizzo.leeds-art.ac.uk");  
     ldapConnection.Path               = "LDAP://OU=staffusers,DC=leeds-art,DC=ac,DC=uk";  
     ldapConnection.AuthenticationType = AuthenticationTypes.Secure;  
     return ldapConnection;  
  }  

I just have the Hostname and the IP Address of our Active Directory Server. What does DC=xxx,DC=xx and so on mean?

Answer 1

DC is your domain. If you want to connect to the domain example.com than your dc's are: DC=example,DC=com

You actually don't need any hostname or ip address of your domain controller (There could be plenty of them).

Just imagine that you're connecting to the domain itself. So for connecting to the domain example.com you can simply write

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://example.com");

And you're done.

You can also specify a user and a password used to connect:

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://example.com", "username", "password");

Also be sure to always write LDAP in upper case. I had some trouble and strange exceptions until I read somewhere that I should try to write it in upper case and that solved my problems.

The directoryEntry.Path Property allows you to dive deeper into your domain. So if you want to search a user in a specific OU (Organizational Unit) you can set it there.

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://example.com");
directoryEntry.Path = "LDAP://OU=Specific Users,OU=All Users,OU=Users,DC=example,DC=com";

This would match the following AD hierarchy:

• com
  • example
    • Users
      • All Users
        • Specific Users

Simply write the hierarchy from deepest to highest.

Now you can do plenty of things

For example search a user by account name and get the user's surname:

DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://example.com");
DirectorySearcher searcher = new DirectorySearcher(directoryEntry) {
    PageSize = int.MaxValue,
    Filter = "(&(objectCategory=person)(objectClass=user)(sAMAccountName=AnAccountName))"
};

searcher.PropertiesToLoad.Add("sn");

var result = searcher.FindOne();

if (result == null) {
    return; // Or whatever you need to do in this case
}

string surname;

if (result.Properties.Contains("sn")) {
    surname = result.Properties["sn"][0].ToString();
}