using System.Reflection;
using System.DirectoryServices;
....
DirectoryEntry ent = new DirectoryEntry("LDAP://CN=My
User,DC=Fabrikam,DC=com");
Object ads = ent.NativeObject;
Type type = ads.GetType();
String firstName = (string) type.InvokeMember("FirstName",
BindingFlags.GetProperty, null, ads, null);
String lastName = (string) type.InvokeMember("LastName",
BindingFlags.GetProperty, null, ads, null);