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Hi.
I now know how to ask my question I have been trying to find out, without confusing people.
All I would like to do is take a string of digits
"123456789"
and get its byte representation (hex) value.
The above, 123456789 entered into the calculator gives :
75BCD15
How would I do that in c#
There, finaly I think I have put what I am trying (desperatly) to do. sorry for all the posts and proberbly need to say sorry for being so confusing.
Thank you in advance
Steve
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Parse it as an int (or long if you expect it to be that big)
Then do something like string.Format("{0:X}", value) or value.ToString("X")
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Thank you.
Yes, that works, but the string will be 41 digits long and I do not what to use bignum or anything.
I am trying to get this function to work, it did in c++, I have modified it but it produces the wrong hex value and I do not know why.
static int decodeSerial(String serial, byte[] result, int ResLen)
{
int m;
int digit;
Array.Clear(result, 0, ResLen);
for (int i = 0; i < serial.Length; i++)
{
digit = serial[i] - '0';
m = 0;
do
{
digit += result[m] * 10;
result[m++] = (byte)(digit % 255);
digit >>= 8;
}
while (m < ResLen);
}
return 0;
}
Thank you
Steve
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I'm not claiming it is anywhere near the optimum, I mimicked your code for as much as I liked it.
Given full freedom I would return a byte array of variable length and never have to signal an overflow.
private static void runAllTests() {
test("1");
test("1000");
test("1000000");
test("1000000000");
long j=1;
for(long i=0; i<63; i++) {
test(j.ToString());
j+=j;
}
test("-1");
test("12345678901234567890123456789012345678901234567890123456789012345678901234567890");
}
private static void test(string decimalDigits) {
try {
byte[] bytes=decodeSerial(decimalDigits, 10);
string s=decimalDigits+" = ";
foreach (byte b in bytes) s+=" "+((int)b).ToString("X2");
log(s);
} catch (Exception exc) {
log(exc.ToString());
}
}
private static byte[] decodeSerial(string decimalDigits, int numberOfBytes) {
byte[] bytes=new byte[numberOfBytes];
foreach (char c in decimalDigits) {
int digit="0123456789".IndexOf(c);
if (digit<0) throw new ArgumentException("bad char in decodeSerial("+decimalDigits+")");
for (int m=0; m< numberOfBytes; m++) {
digit+=bytes[m]*10;
bytes[m]=(byte)(digit&0xFF);
digit>>=8;
}
if (digit!=0) throw new OverflowException("decodeSerial("+decimalDigits+","+numberOfBytes+")");
}
return bytes;
}
FYI: log(string s) is any method that somehow outputs a string, could be as simple as Console.WriteLine(s);
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Thank you very much.
Obviosly I take it you now understand what I meant originaly?
It was hard to explain lol.
thank you again,
Steve
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stephen.darling wrote: It was hard to explain
Not really, however you made it rather hard to understand. I summarized it in a three-line comment (I just added an example).
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Yes you did
Now I just need to figure out a function that will do the reverse, take the byte array and product the original string!
Do I dare ask for more help? 
Steve
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Yes you dare, and no you're not going to get a solution from me.
As far as I can tell, you haven't learned a single thing yet, all I saw you do was copy some C++ code,
then massage it blindly until it compiled well and ran all wrong. It is time to learn and understand what is really going on.
If you want more help, you write code yourself, debug it, and when stuck, post here, and we all will help you.
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That is fair enough.
I am trying, and I have managed to learn some things from my books. I have managed to write my first little game that works well.
I dont what you to write the code for me, just point me in the right direction.
When it comes to this area it is not covered in my books, and because I dont know what search terms to use for this kind of programing (You see how hard it was to explain what I wanted to do) I find it difficult to find out.
I will try and plod on and lear, hopefully I didnt offend, or worse still come across as a lazy person not willing to learn on my own.
Also, if I may add, I tried my best to rewrite the code so that I didnt have to ask anyone in the first place, and I have been on with this problem for over 2 months before asking for help.
Thank you again for your time.
Steve
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You're welcome.
Seems like we will meet again.
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stephen.darling wrote: I have been on with this problem for over 2 months before asking for help
I admire your ambition, but maybe it's time for you to tackle simpler problems for the time being (before you burn out on problems beyond your capability). I saw nothing in your posts that indicated you were taking a logical approach to solving this problem. You didn't post that you had tried debugging it incrementally by outputting values as the algorithm ran. You didn't post that you tried with very simple values and made them more and more complex until you could reproduce the bug. You didn't describe the mathematical reasoning behind the algorithm (if you don't know how it's supposed to work, how are you supposed to make it work). You couldn't even describe what it is you were so desperately trying to do for the past 2 months (if you can't define the question, you can't solve the problem). Seriously, take a step back and take another look at the basics. Finding a mentor would be good; I mean a real, live person... not some random people on a forum. A teacher, a friend who is good at programming, or even a tutor at your school (if you are going to school) would be great. It would be a shame to waste all the passion you seem to have on reaching too high too quickly and experiencing only failure. You need to experience success if you are going to keep doing programming. Good luck.
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Is that the new beginner assignment?
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What do you mean?
Do you mean is this an assignment from school?
If that is what you meant, no, it is not.
I am aged 31. I am in full time education, reading a degree in biomedical science at a university in the UK, and c# programming is simply a hobby.
aspdotnetdev, Yes, I suppose you have a point. I have indeed bit off more than I can chew. What can I say, I am very impatient, and want to know to much to quick 
Time to start from the beginning I suppose.
Thank you everyone.
Kind regards,
Steve
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Assuming you are starting with a number (n in the example below) you can just do:
Convert.ToString(n, 16)
If you have a String rather than an number, convert it to an int first.
Seems a bit of an obvious answer, so maybe I've misunderstood your question.
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This is like the fifth post on the same topic. What wasn't mentioned is that the number can be very large (larger than a long can hold).
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Hi again everyone.
I figured out how to represent a string of digits as its byte encoding representation, by converting c++ code that does just this, but it is producing the wrong result and I dont know why...
Here is the working code from my app...
private void button1_Click(object sender, EventArgs e)
{
string serialNumber = ("123456789");
byte[] output = new byte[5];
int result = decodeSerial(serialNumber, output, 5);
}
static int decodeSerial(string serial, byte[] result, int ResLen)
{
int m;
int digit, aux;
Array.Clear(result, 0, ResLen);
for (int i = 0; i < serial.Length ; i ++)
{
digit = serial[i] - '0';
aux = digit;
m = 0;
do
{
aux += result[m] * 10;
result[m++] = (byte)(aux % 255);
aux >>= 8;
}
while (m < ResLen);
digit *= 2;
}
return 0;
}
}
Now, when I pass in the string "123456789" I should get the byte encoding of:
0x75, 0xBC, 0xD1, 0x05 (Workis on my calculator AND it worked in a c++ app with the ORIGINAL c++ code,
But in this app, it produces the following hex data...
45, 9A, 71, 07
I def want to use this function, as when it works, I will be passing in a string of digits 41 in length, and besides, the original c++ function worked many months before when I tried it, but now I am using c#.
I would also prefer not to use bignum or any other type of function.
Can anyone help out please?
Thank you
Steve
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stephen.darling wrote: while (m < ResLen);
I wasn't going to look at all this in any detail, however that line struck me as a meaningless statement as it repeats nothing until the condition becomes false. You may want to drop the semi-colon, or have to change something else altogether.
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Hi.
What do you mean by 'drop the semi colon'?
If I remove the semi colon, I get an error telling me semi colon is required.
Also, if You dont mind me asking, how does it do nothing, as I step through my code, something is definatly happening, and I do end up with a number of bytes, just not what I get from my calculator.
Thank you again, Luc Pattyn.
Steve
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sorry, my mistake. I overlooked the "do" keyword. 
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Why are you multiplying digit by 2 at the end of the for loop only to throw away the value and re-assign the value of digit at the top of the for loop? Why does decodeSerial return in rather than void if the value is meaningless? Why are you subtracting a string? What is the purpose of the aux variable when it is never different from digit during processing?
There are so many things wrong with this code that I really think you need to give up on this algorithm and start from scratch with something simpler.
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I dont know is the short answer 
I am trying my best, I got that code to work in the c++ version.
All I want to do is encode a string of digits to a byte array encoding.
The string is "123456789"
If I enter 123456789 on my calculator and press the "hex" button, it gives:
459A717
And that is what I want my code to do 
Steve
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stephen.darling wrote: If I enter 123456789 on my calculator and press the "hex" button, it gives:
459A717
All you need to do is convert your string to an integer then format that integer as a hex value, the same as you would in C++. See here[^] for information on formatting your output.
It's time for a new signature.
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That isn't what he is doing. That hex button on his calculator doesn't do what the hex button does in windows calculator. Or he is giving bad example data just to confuse people and prevent them from helping (123456789 is not 0x459A717). Also, he needs to handle numbers larger than an int64.
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Yes I figured that out by looking at the other question. A pity he didn't describe the full problem in the first place.
It's time for a new signature.
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T M Gray wrote: Why are you subtracting a string?
The code actually subtracts a char from another char. Give this a try:
MessageBox.Show(("5"[0] - '0' + 1).ToString());
Perhaps not as intuitive as int.Parse, but it might just be faster.
The rest of your criticisms are valid.
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