/// <summary>    
  /// 获取IPv4地址    
  /// </summary>    
  /// <returns>
  </returns>  
  public static string GetIP4Address(HttpRequest request = null)    
  {      
  Func<IPAddress, bool> f = e => e.AddressFamily.ToString() == "InterNetwork";      
  IPAddress ipa = Dns.GetHostAddresses((request
  ?? HttpContext.Current.Request).UserHostAddress).FirstOrDefault(f)        
  ?? Dns.GetHostAddresses(Dns.GetHostName()).FirstOrDefault(f);      
  if (ipa != null)     
  {       
  return ipa.ToString();    
  }      
  return HttpContext.Current.Request.UserHostAddress;   
  }