IP格式检查、IP -- INT 转换

 public static bool CheckIPAddress(string IP)
        {
            string pattern = @"(((\d{1,2})|(1\d{2})|(2[0-4]\d)|(25[0-5]))\.){3}((\d{1,2})|(1\d{2})|(2[0-4]\d)|(25[0-5]))";
            System.Text.RegularExpressions.Regex regex = new System.Text.RegularExpressions.Regex(pattern);
            if (regex.Match(IP).Success)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        private static long IpToInt(string ip)
        {
            char[] separator = new char[] { '.' };
            if (ip.Split(separator).Length == 3)
            {
                ip = ip + ".0";
            }
            string[] strArray = ip.Split(separator);
            long num2 = ((long.Parse(strArray[0]) * 0x100L) * 0x100L) * 0x100L;
            long num3 = (long.Parse(strArray[1]) * 0x100L) * 0x100L;
            long num4 = long.Parse(strArray[2]) * 0x100L;
            long num5 = long.Parse(strArray[3]);
            return (((num2 + num3) + num4) + num5);
        }

        private static string IntToIP(long ip_Int)
        {
            long num = (long)((ip_Int & 0xff000000L) >> 0x18);
            if (num < 0L)
            {
                num += 0x100L;
            }
            long num2 = (ip_Int & 0xff0000L) >> 0x10;
            if (num2 < 0L)
            {
                num2 += 0x100L;
            }
            long num3 = (ip_Int & 0xff00L) >> 8;
            if (num3 < 0L)
            {
                num3 += 0x100L;
            }
            long num4 = ip_Int & 0xffL;
            if (num4 < 0L)
            {
                num4 += 0x100L;
            }
            return (num.ToString() + "." + num2.ToString() + "." + num3.ToString() + "." + num4.ToString());
        }