ADO.NET

OleDbConnection conn = new OleDbConnection();

conn.ConnectionString = "Provider=ADSDSOObject; Data Source=LDAP://localhost/O=SMACC"; 

conn.Open();

OleDbCommand command= conn.CreateCommand(); 

command.

command.CommandText = "< LDAP://localhost/O=SMACC>;(objectClass=user);cn,givenName;subtree"; 

OleDbDataReader reader= command.ExecuteReader();

while (reader.Read()) 

{

Console.WriteLine(reader.GetString(0)); 

}