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BitConverter.GetBytes(a + 1000000*b)
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Hi,
Sorry, this produces a different result than required.
uint val1 = 583;
uint val2 = 728439;
I should have 583728439, which sould be (in bytes) 0x22CAFD37.
Am I doing something wrong?
Thank you,
Stephen
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You can combine them using division and modulo operations:
const uint shift = 1000000;
uint val1 = 539;
uint val2 = 666666;
uint combined = (val1 * shift) + val2;
uint restore_val1 = combined / shift;
uint restore_val2 = combined % shift;
As for getting the byte array, you can use the BitConverter:
byte[] combined_bin = BitConverter.GetBytes(combined);
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Thank you very much.
That works perfect.
Steve
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Hi.
The following function was taken from c++ code, and I have tried to adapt it for my c# code, however, I am not sure if it is doing the same thing?
The full c++ function is...
void ShowProdKey(unsigned char *ProdKey)
{
unsigned int Val1, Val2;
Val1 = *(unsigned int *)ProdKey;
Val1 &= 0x7fffffff;
Val1 >>= 1;
Val2 = CheckDigit(Val1 % 1000000);
Val1 /= 1000000;
printf("Your product ID should be XXXXX-%.3u-%.7u-XXXXX.\n", Val1, Val2);
}
and my adapted function is the following (it works as in as far as it is producing a result which looks correct, but I am unsure if the changed part of the function is doing the same as in the above code)
void ShowProdKey(byte[] prodKey)
{
uint val1, val2;
val1 = BitConverter.ToUInt32(prodKey, 0);
val1 &= 0x7fffffff;
val1 >>= 1;
val2 = CheckDigit(val1 % 1000000);
val1 /= 1000000;
string output = ("");
output = val1.ToString();
output += val2.ToString();
MessageBox.Show(output);
}
So the part I changed was this in c++
Val1 = *(unsigned int *)ProdKey;
To this...
val1 = BitConverter.ToUInt32(prodKey, 0);
The output should be a double word formatted something like...
000 - 0000000
My version does produce a value like this, so I think it may be doing the same thing?
Also, how would I write code to reverse the function?
Or, in other words, the above function takes 4 bytes and produces a DWORD, which it formats into two unsigned ints...
How would I write a function that would take two unsigned ints, and produce a DWORD, and then encode that into 4 bytes, the reverse of the above function?
Thank you VERY much for your help...
Stephen
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stephen.darling wrote: Val1 = *(unsigned int *)ProdKey;
Can probably be done with unsafe code.
stephen.darling wrote: Val1 >>= 1;
Probably makes it non-reversible (except with a 50/50 probability of being correct).
stephen.darling wrote: CheckDigit
What does that do?
What is it trying to do? It doesn't seem to use all the bits that are sent in.
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Hi,
Well, using that function, if the 4 bytes are:
0x22CAFD37, the function should produce the following number:
583728439
Now, using the c++ version it works correct, but my c# version does not produce the correct value, it does produce a 9 digit number, but not that one.
However, if I try to use:
Val1 = *(unsigned int *)ProdKey;
in my c# version, it wont compile, so not sure if the code I changed is doing something else?
To answer what it is, let me explain...
My keygenerator generates the above 9 digit number, as a kind of product ID value, and encodes it into a 4 byte array to build part of a serial number..
When the serial number is entered into my application, the 4 bytes are decoded back into a dword, and the above function formats it into the 9 digits shown, and my app checks them,
It is working, and 9 digits are produced, but they are incorrect????
Also, how do I reverse the code to get two int values into one DWORD, and then encode it back into a 4 byte array?
Thank you,
Stephen
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The BitConverter code looks correct. (Just like a cast in C, though, it will give a different answer if the machine has the opposite endianness.) Your code is doing more than just that – what is CheckDigit doing?
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Hi.
Thank you. So How do I check and/or fix the endian?
If it helps, the text I have says that it is stored in little endian byte order, and the following four bytes: 0x22CAFD37 should produce 583728439.
The checkdigit function then calculates and adds a checkdigit so that the above is then:
5837284392
here is the code for check digit...
<pre>uint CheckDigit(uint val)
{
uint sum, copy;
sum = 0;
copy = val;
while (copy !=0)
{
sum += copy % 10;
copy /= 10;
}
return val * 10 + 7 - (sum % 7);
}</pre>
thank you
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On my machine (Windows 32 bit) I'm getting the opposite order:
$BitConverter:GetBytes(5)
(5 0 0 0)
$BitConverter:GetBytes(583728439)
(55 253 202 34)
{x: x:ToString "X2"}¨($BitConverter:GetBytes(583728439))
(37 FD CA 22)
This should be the same in C++, however.
(I can't so easily test the other way around, my toy language doesn't understand about bytes as a native type at the moment.)
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OK,thank you.
I will keep trying on with this.
Steve
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Hi All !
myVal=1365 , and in the String.Format i want to get only Two last digit number(65) .
using with String.Format , any body help to this :
String.Format("{0:00}",myVal); but the output is : 1365
Regards !
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thanks , but is it possible with String Format
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Not to my knowledge. 
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The string.Format method is used to get a string representation of an object in the specified format. It is not intended to change the value of its arguments. You can use
int m = n % 100; to get the last two digits of the number. If at all you have to use strings to achieve the same answer, you can do this
string m = n.ToString().SubString(n.ToString().Length - 2);
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if 2 users connect to access and run query that check the last number
increase this number and insert record to database.
Who gets the priority ?
why i see 2 duplicate records with the same number ?
thanks in advance
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It sounds like you need a transaction; that's what they're for.
I also don't recommend Access. 
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What you need in this case is an auto-incremented number, such as a primary key, rather than relying on a number field which must be manually incremented. You could also increment the number when inserting the record, not before.
I also agree with PIEBALDconsult, don't use Access. SQL Express is FREE and more robust than Access in multi-user scenarios. It also easier to upgrade to a full SQL Server implementation when necessary.
I know the language. I've read a book. - _Madmatt
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Mark Nischalke wrote: auto-incremented number
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I need to copy data from mysql via xml to access database. connected to the ProgressBar. database contains multiple tables. is not a tutorial on it some? Thank you for your help. Mark
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