Get hire Date for all users from Active directory

using (var context = new PrincipalContext(ContextType.Domain, "yourdomain.com")) 
{
using (var searcher = new PrincipalSearcher(new UserPrincipal(context))) 
  { 
 foreach (var result in searcher.FindAll())
 { 
   DirectoryEntry de = result.GetUnderlyingObject() as DirectoryEntry; 
   Console.WriteLine("First Name: " + de.Properties["givenName"].Value); 
   Console.WriteLine("Last Name : " + de.Properties["sn"].Value); 
   Console.WriteLine("SAM account name   : " + de.Properties["samAccountName"].Value); 
   Console.WriteLine("User principal name: " + de.Properties["userPrincipalName"].Value);
 Console.WriteLine(); 
  } 
 }
}
Console.ReadLine();



i tried the above code but that is not working with the hire date and birthday column because these are non-mapped column.
can you help me with that?