Get IP address from notation or hostname

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.Text.RegularExpressions;
using System.Globalization;
using System.Net.Sockets;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.Net.NetworkInformation;

namespace Lidgren.Network
{
  public static class NetUtility
  {
    private static Regex s_regIP;

    public static IPAddress Resolve(string ipOrHost)
    {
      if (string.IsNullOrEmpty(ipOrHost))
        throw new ArgumentException("Supplied string must not be empty", "ipOrHost");

      ipOrHost = ipOrHost.Trim();

      if (s_regIP == null)
      {
        string expression = "\\b(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\b";
        RegexOptions options = RegexOptions.Compiled;
        s_regIP = new Regex(expression, options);
      }

      IPAddress ipAddress = null;
      if (s_regIP.Match(ipOrHost).Success && IPAddress.TryParse(ipOrHost, out ipAddress))
        return ipAddress;

      IPHostEntry entry;
      try
      {
        entry = Dns.GetHostEntry(ipOrHost);
        if (entry == null)
          return null;

        foreach (IPAddress ipCurrent in entry.AddressList)
        {
          string sIP = ipCurrent.ToString();
          bool isIP = s_regIP.Match(sIP).Success && IPAddress.TryParse(sIP, out ipAddress);
          if (isIP)
            break;
        }
        if (ipAddress == null)
          return null;

        return ipAddress;
      }
      catch (SocketException ex)
      {
        if (ex.SocketErrorCode == SocketError.HostNotFound)
        {
          //LogWrite(string.Format(CultureInfo.InvariantCulture, "Failed to resolve host '{0}'.", ipOrHost));
          return null;
        }
        else
        {
          throw;
        }
      }
    }

    private static NetworkInterface GetNetworkInterface()
    {
      IPGlobalProperties computerProperties = IPGlobalProperties.GetIPGlobalProperties();
      if (computerProperties == null)
        return null;

        NetworkInterface[] nics = NetworkInterface.GetAllNetworkInterfaces();
      if (nics == null || nics.Length < 1)
        return null;

      foreach (NetworkInterface adapter in nics)
      {
        if (adapter.OperationalStatus != OperationalStatus.Up)
          continue;
        if (adapter.NetworkInterfaceType == NetworkInterfaceType.Loopback || adapter.NetworkInterfaceType == NetworkInterfaceType.Unknown)
          continue;
        if (!adapter.Supports(NetworkInterfaceComponent.IPv4))
          continue;

        return adapter;
      }
      return null;
    }

  }
}