/// <summary>  /// 獲取客戶端IP  /// </summary>  /// <returns></returns>  public static string GetClientIpAddress()    {      var httpContext = HttpContext.Current;      if (httpContext.Request.ServerVariables == null)      {        return null;      }      var clientIp = httpContext.Request.ServerVariables["HTTP_X_FORWARDED_FOR"] ??              httpContext.Request.ServerVariables["REMOTE_ADDR"];      try      {        foreach (var hostAddress in Dns.GetHostAddresses(clientIp))        {          if (hostAddress.AddressFamily == AddressFamily.InterNetwork)          {            return hostAddress.ToString();          }        }        foreach (var hostAddress in Dns.GetHostAddresses(Dns.GetHostName()))        {          if (hostAddress.AddressFamily == AddressFamily.InterNetwork)          {            return hostAddress.ToString();          }        }      }      catch (Exception ex)      {      }      return clientIp;    }  /// <summary>  /// ip是否在ip空間內  /// </summary>  /// <param name="ip"></param>  /// <param name="ipSection"></param>  /// <returns></returns>  public static Boolean ipExistsInRange(String ip, String ipSection)  {    ipSection = ipSection.Trim();    ip = ip.Trim();    int idx = ipSection.IndexOf('-');    String beginIP = ipSection.Substring(0, idx);    String endIP = ipSection.Substring(idx + 1);    return getIp2long(beginIP) <= getIp2long(ip) && getIp2long(ip) <= getIp2long(endIP);  }  public static long getIp2long(String ip)  {    ip = ip.Trim();    String[] ips = ip.Split('.');    long ip2long = 0L;    for (int i = 0; i < 4; ++i)    {      ip2long = ip2long << 8 | Int64.Parse(ips[i]);    }    return ip2long;  }  public static long getIp2long2(String ip)  {    ip = ip.Trim();    String[] ips = ip.Split('.');    long ip1 = Int64.Parse(ips[0]);    long ip2 = Int64.Parse(ips[1]);    long ip3 = Int64.Parse(ips[2]);    long ip4 = Int64.Parse(ips[3]);    long ip2long = 1L * ip1 * 256 * 256 * 256 + ip2 * 256 * 256 + ip3 * 256 + ip4;    return ip2long;  }