Role based authendication

WindowsIdentity ident = WindowsIdentity.GetCurrent();
WindowsPrincipal user = new WindowsPrincipal(ident);
string username = StripDomainFromUserName(user.Identity.Name);

using (DirectoryEntry de = new DirectoryEntry("LDAP://" + StripDomain(user.Identity.Name)))
{
    using (DirectorySearcher adSearch = new DirectorySearcher(de))
    {
        adSearch.Filter = "(DomAccountName=" + username + ")";
        SearchResult adSearchResult = adSearch.FindOne();

        UserID = username;
        UserName = StripLoggedUserName(adSearchResult.Path);
    }
}