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1297

answers:

3

How can I generate a random hexadecimal number with a length of my choice using C#?

+8  A: 
static Random random = new Random();
public static string GetRandomHexNumber(int digits)
{
    byte[] buffer = new byte[digits / 2];
    random.NextBytes(buffer);
    string result = String.Concat(buffer.Select(x => x.ToString("X2")).ToArray());
    if (digits % 2 == 0)
        return result;
    return result + random.Next(16).ToString("X");
}
Mehrdad Afshari
+3  A: 
    Random random = new Random();
    int num = random.Next();
    string hexString = num.ToString("X");

random.Next() takes arguments that let you specify a min and a max value, so that's how you would control the length.

womp
It'll work only if `length <= 8` as `int.MaxValue` fits in 8 hex digits.
Mehrdad Afshari
If he really does want the hex string to be of a length of his choice, you will need code that calculates the minimum number with hex length 'x' and maximum with length 'x'.
colithium
Yep. I left that out on purpose, but you would basically just have to do a conversion on 0xF? ('scuse my regular expression) to find whatever integer matched your desired length.
womp
+2  A: 

Depends on how random you want it, but here are 3 alternatives: 1) I usually just use Guid.NewGuid and pick a portion of it (dep. on how large number I want).

2) System.Random (see other replies) is good if you just want 'random enough'.

3) System.Security.Cryptography.RNGCryptoServiceProvider

KristoferA - Huagati.com
Slicing up a GUID seems like a real bad idea to me. They're only unique taken as a whole. Many bits of a GUID certainly don't qualify as random.
spender
@spender is correct, for instance many GUIDs contain the MAC address of the PC generating them.
Eric Haskins
Eh, no, the mac-address based guids were retired back in 2000-ish as they were considered a potential security issue. GUIDs are now generated by a random number generator (122 bits random, 6 bits non-random). Either way, using a 32 (or more) bit slice of a guid gives a more random number than System.Random.That is - unless you call UuidCreateSequential which was added for backwards compatibility in case anyone want old style guids, but that is a different story.
KristoferA - Huagati.com
Mora random than Random?
spender
Yes. See the documentation for System.Random at http://msdn.microsoft.com/en-us/library/system.random.aspx
KristoferA - Huagati.com
I learned something this weekend.
spender