Getting username from Active Directory

principal.cs

using System;
using System.DirectoryServices;
using System.Security.Principal;
using System.Web.UI;

namespace BookWeb
{
  public partial class Main : MasterPage
    {
      protected void Page_Load(object sender, EventArgs e)
      {
        string fullname = GetFullName(Page.User);
        lblName.Text = fullname;
      }

      private static string GetFullName(IPrincipal user)
      {
        string name = string.Empty;

        if (user == null) return name;

        string ldapName = user.Identity.Name.Split('\\')[1];
        DirectoryEntry entry = new DirectoryEntry("LDAP://DC=Woolpertinc,DC=local");
        DirectorySearcher searcher = new DirectorySearcher(entry);
        searcher.Filter = string.Format("(sAMAccountName={0})", ldapName);
        searcher.PropertiesToLoad.Add("givenName"); // given, or first, name
        searcher.PropertiesToLoad.Add("sn"); // surname
        SearchResult result = searcher.FindOne();
        
        if (result != null)
        {
          name = string.Format("{0} {1}", result.Properties["givenName"][0], result.Properties["sn"][0]);
        }

        return name;
     }
  }
}