public static long IP2Long(string ip)
{
  string[] ipBytes;
  double num = 0;
  if(!string.IsNullOrEmpty(ip))
  {
   ipBytes = ip.Split('.');
   for (int i = ipBytes.Length - 1; i >= 0; i--)
   {
   num += ((int.Parse(ipBytes[i]) % 256) * Math.Pow(256, (3 - i)));
   }
  }
  return (long)num;
}

long start = IP2Long("127.0.0.1");
long end = IP2Long("127.0.0.255");
long ipAddress = IP2Long("127.0.1.253");
bool inRange = (ipAddress >= start && ipAddress <= end);
if (inRange){
 //IP Address fits within range!
}