string values to byte array without converting

Question

I'm trying to put the values of a string into a byte array with out changing the characters. This is because the string is in fact a byte representation of the data.

The goal is to move the input string into a byte array and then convert the byte array using:

string result = System.Text.Encoding.UTF8.GetString(data);

I hope someone can help me although I know it´s not a very good description.

EDIT: And maybe I should explain that what I´m working on is a simple windows form with a textbox where users can copy the encoded data into it and then click preview to see the decoded data.

EDIT: A little more code: (inputText is a textbox)

    private void button1_Click(object sender, EventArgs e)
    {
        string inputString = this.inputText.Text;
        byte[] input = new byte[inputString.Length];
        for (int i = 0; i < inputString.Length; i++)
        {
            input[i] = inputString[i];
        }
        string output = base64Decode(input);
        this.inputText.Text = "";
        this.inputText.Text = output;
    }

This is a part of a windows form and it includes a rich text box. This code doesn´t work because it won´t let me convert type char to byte. But if I change the line to :

    private void button1_Click(object sender, EventArgs e)
    {
        string inputString = this.inputText.Text;
        byte[] input = new byte[inputString.Length];
        for (int i = 0; i < inputString.Length; i++)
        {
            input[i] = (byte)inputString[i];
        }
        string output = base64Decode(input);
        this.inputText.Text = "";
        this.inputText.Text = output;
    }

It encodes the value and I don´t want that. I hope this explains a little bit better what I´m trying to do.

EDIT: The base64Decode function:

    public string base64Decode(byte[] data)
    {
        try
        {
            string result = System.Text.Encoding.UTF8.GetString(data);
            return result;
        }
        catch (Exception e)
        {
            throw new Exception("Error in base64Decode" + e.Message);
        }
    }

The string is not encoded using base64 just to be clear. This is just bad naming on my behalf.

Note this is just one line of input.

I've got it. The problem was I was always trying to decode the wrong format. I feel very stupid because when I posted the example input I saw this had to be hex and it was so from then on it was easy. I used this site for reference: http://msdn.microsoft.com/en-us/library/bb311038.aspx

My code:

     public string[] getHexValues(string s)
     {
        int j = 0;
        string[] hex = new String[s.Length/2];
        for (int i = 0; i < s.Length-2; i += 2)
        {
            string temp = s.Substring(i, 2);
            this.inputText.Text = temp;
            if (temp.Equals("0x")) ;
            else
            {
                hex[j] = temp;
                j++;
            }
        }
        return hex;
    }

    public string convertFromHex(string[] hex)
    {
        string result = null;
        for (int i = 0; i < hex.Length; i++)
        {
            int value = Convert.ToInt32(hex[i], 16);
            result += Char.ConvertFromUtf32(value);
        }
        return result;
    }

I feel quite dumb right now but thanks to everyone who helped, especially @Jon Skeet.

Answer 1

Are you saying you have something like this:

string s = "48656c6c6f2c20776f726c6421";

and you want these values as a byte array? Then:

public IEnumerable<byte> GetBytesFromByteString(string s) {
    for (int index = 0; index < s.Length; index += 2) {
        yield return Convert.ToByte(s.Substring(index, 2), 16);
    }
}

Usage:

string s = "48656c6c6f2c20776f726c6421";
var bytes = GetBytesFromByteString(s).ToArray();

Note that the output of

Console.WriteLine(System.Text.ASCIIEncoding.ASCII.GetString(bytes));

is

Hello, world!

You obviously need to make the above method a lot safer.

Answer 2

Encoding has the reverse method:

byte[] data  = System.Text.Encoding.UTF8.GetBytes(originalString);

string result = System.Text.Encoding.UTF8.GetString(data);

Debug.Assert(result == originalString);

But what you mean 'without converting' is unclear.