C# 生成字符串的 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();
}