Question

On MSDN it mentions GetHostByName is obsolete. The replacement is GetHostEntry. What are their difference?

Answer 1

It looks like GetHostEntry does a little more error checking and also supports Network Tracing

GetHostByName Decompiled:

public static IPHostEntry GetHostByName(string hostName)
{
  if (hostName == null)
    throw new ArgumentNullException("hostName");
  Dns.s_DnsPermission.Demand();
  IPAddress address;
  if (IPAddress.TryParse(hostName, out address))
    return Dns.GetUnresolveAnswer(address);
  else
    return Dns.InternalGetHostByName(hostName, false);
}

GetHostEntry Decompiled:

public static IPHostEntry GetHostEntry(string hostNameOrAddress)
{
  if (Logging.On)
    Logging.Enter(Logging.Sockets, "DNS", "GetHostEntry", hostNameOrAddress);
  Dns.s_DnsPermission.Demand();
  if (hostNameOrAddress == null)
    throw new ArgumentNullException("hostNameOrAddress");
  IPAddress address;
  IPHostEntry ipHostEntry;
  if (IPAddress.TryParse(hostNameOrAddress, out address))
  {
    if (((object) address).Equals((object) IPAddress.Any) || ((object) address).Equals((object) IPAddress.IPv6Any))
      throw new ArgumentException(SR.GetString("net_invalid_ip_addr"), "hostNameOrAddress");
    ipHostEntry = Dns.InternalGetHostByAddress(address, true);
  }
  else
    ipHostEntry = Dns.InternalGetHostByName(hostNameOrAddress, true);
  if (Logging.On)
    Logging.Exit(Logging.Sockets, "DNS", "GetHostEntry", (object) ipHostEntry);
  return ipHostEntry;
}