Check if IP Address belongs to a given CIDR

private static bool IsInRange(IPAddress ip, string cidr)
        {
            var parts = cidr.Split('/');

            var ipAddr = BitConverter.ToInt32(ip.GetAddressBytes(), 0);
            var cidrAddr = BitConverter.ToInt32(IPAddress.Parse(parts[0]).GetAddressBytes(), 0);
            // Note: When shifting a negative number all the least segnificant bits will
            // be changed to zero e.g: -1 << 1 = 1111 11110 nothing this is signed byte
            var cidrMask = IPAddress.HostToNetworkOrder(-1 << (32 - int.Parse(parts[1]))); // this is kinda hack to convert cidr mask to it's real representation e.g: /8 = 1111 1111. 0000 0000 . 0000 0000 . 0000 0000

            // this is checking if the given addres is in same network as the cidr addresss
            // https://en.wikipedia.org/wiki/Subnetwork (keyword: "bitwise")
            // applying bitwise AND to a ip and mask yield back the network address.
            return ((ipAddr & cidrMask) == (cidrAddr & cidrMask));

            // NOTE: About shiftting negative
            // example cidr mask == 8
            // -1 << (32 - 8)
            // -1 << 24
            // a signed integer when is negative it's represented like:
            // 1st byte/octet | 2nd byte/octet | 3rd byte/octet |4th byte/octet)
            // (1111 1111) (1111 1111) (1111 1111) (1111 1111)
            // most significant byte to least significant
        }
// note: code found in Vinchuca botnet project