private Byte GetCheckSum(Byte[] bytes)
{
	Byte checksum = 0x00;
 
	foreach (byte bt in bytes)
	{
		checksum ^= bt;
	}
 
	return checksum;
}

private static string CheckSum(string message)
{
? ? char[] chars = message.ToCharArray();
? ? int checksum = 0;
? ? for (int i = 0; i < chars.Length; i++)
? ? {
? ? ? ? checksum += (int)chars[i];
? ? }
? ? checksum = (~checksum & 0xFFFF) + 0x0001;
? ? return Convert.ToString(checksum, 16).ToUpper();
}