public static byte[] addBytes(byte[] data1, byte[] data2, int validLen)
    {
        if (validLen <= 0)
        {
            throw new Exception("Data2 cannot be null!");
        }

        if (data1 == null || data1.Length == 0)
        {
            byte[] buffer = new byte[validLen];
            Buffer.BlockCopy(data2, 0, buffer, 0, validLen);
            return buffer;
        }

        byte[] data3 = new byte[data1.Length + validLen];
        Buffer.BlockCopy(data1, 0, data3, 0, data1.Length);
        Buffer.BlockCopy(data2, 0, data3, data1.Length, validLen);
        return data3;
    }