如何将十六进制字符串转换为C＃中ASCII值相同的字符串？

Question

Assume that I have a string containing a hex value. For example:

string command "0xABCD1234";

How can I convert that string into another string (for example, string codedString = ... ) such that this new string's ASCII-encoded representation has the same binary as the original strings contents ?

The reason I need to do this is because I have a library from a hardware manufacturer that can transmit data from their piece of hardware to another piece of hardware over SPI . Their functions take strings as an input, but when I try to send "AA" I am expecting the SPI to transmit the binary 10101010, but instead it transmits the ascii representation of AA which is 0110000101100001.

Also, this hex string is going to be 32 hex characters long (that is, 256-bits long).

Answer 1

string command = "AA";
int num = int.Parse(command,NumberStyles.HexNumber);
string bits = Convert.ToString(num,2); // <-- 10101010

Answer 2

I think I understand what you need... here is the main code part.. asciiStringWithTheRightBytes is what you would send to your command.

var command = "ABCD1234";
var byteCommand = GetBytesFromHexString(command);
var asciiStringWithTheRightBytes = Encoding.ASCII.GetString(byteCommand);

And the subroutines it uses are here...

static byte[] GetBytesFromHexString(string str)
{
    byte[] bytes = new byte[str.Length * sizeof(byte)];
    for (var i = 0; i < str.Length; i++)
        bytes[i] = HexToInt(str[i]);
        return bytes;
}

static byte HexToInt(char hexChar)
{
    hexChar = char.ToUpper(hexChar);  // may not be necessary

    return (byte)((int)hexChar < (int)'A' ?
        ((int)hexChar - (int)'0') :
        10 + ((int)hexChar - (int)'A'));
}