Generating Random Strings

[Loli]

How would you do it?
I'm doing it like this

        private void button1_Click(object sender, EventArgs e)
        {
            int i = 50;
            Random rnd = new Random();
            while (i-- > 0)
                txtKey.Text = GenerateKey(rnd, 32);
        }

        public string GenerateKey(Random rnd, int Length)
        {
            string charPool = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!£$%^&*";
            StringBuilder sb = new StringBuilder();
            
            while (Length-- > 0)
            sb.Append(charPool[(int)rnd.NextDouble() * charPool.Length]);

            return sb.ToString();
        }

This just returns AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
Any ideas why? Would you do it a different way?

[Darwin226]

How about getting a random number from 0 to 25, add 40 and then get the char from that ASCII?
Shouldn't be hard to make.
(btw, that only generates upper case letters)

[Loli]

Could use array... I suppose...

[Darwin226]

Well, this works. It's C# btw.
[cpp]using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication2 {
class Program {
static void Main(string[] args) {

Random random=new Random();
int i = 0;
while (i < 10) {

int randNum;
if (random.NextDouble() > 0.5) {

randNum = (int)(random.NextDouble() * 25) + 65;
}
else {

randNum = (int)(random.NextDouble() * 25) + 97;
}
Console.Write((char)randNum);
++i;
}
Console.ReadKey();
}
}
}
[/cpp]

Generates a string of 10 chars which are random upper and lower case letters of the English alphabet.

[ZeekyHBomb]

(int)rnd.NextDouble() * charPool.Length
should be
(int)(rnd.NextDouble() * charPool.Length)
else the double is casted into an int and then multiplied by the length, with a chance of 2^24-1 to 1 resulting in 0.
Edit: The probability is wrong, since double has a bunch of NaNs, INFs 'n stuff, but it's still very probably to result in 0 :P

[Darwin226]

-snip-

Wow, very stupid of me.
I didn't realize you commented to the OP.

[Loli]

[QUOTE=ZeekyHBomb;21310303](int)rnd.NextDouble() * charPool.Length
should be
(int)(rnd.NextDouble() * charPool.Length)
else the double is casted into an int and then multiplied by the length, with a chance of 2^24-1 to 1 resulting in 0.
Edit: The probability is wrong, since double has a bunch of NaNs, INFs 'n stuff, but it's still very probably to result in 0 :P[/QUOTE]

Shit, yeah. Damn I'm getting worse at this stuff. Spotting errors was never my thing :rolleyes:

[Kirth]

[QUOTE=Loli;21310873]Shit, yeah. Damn I'm getting worse at this stuff. Spotting errors was never my thing :rolleyes:[/QUOTE]

That should come in due time. Once you've struggled enough with certain errors you should be able to catch and fix them whilst half asleep.

[ShaRose_]

[cpp] private static RandomNumberGenerator rng;
static string GetRandomString(char[] chars,int length)
{
if (length < 1)
return "";
StringBuilder stringBuilder = new StringBuilder(length);
if (rng == null)
rng = RandomNumberGenerator.Create();
byte[] bytes = new byte[length];
rng.GetBytes(bytes);
for (int i = 0; i < length; i++)
stringBuilder.Append(chars[bytes[i]%chars.Length]);
return stringBuilder.ToString();
}[/cpp]

Needs System.Security.Cryptography and System.Text

[editline]12:13AM[/editline]

No, but seriously, why are so many people saying to use doubles? Really?

[editline]12:14AM[/editline]

Oh, and one limitation, chars needs to be under 256 chars. Otherwise, it'll only use the first 256. But that should be easy to fix.

[Loli]

[QUOTE=Kirth;21312160]That should come in due time. Once you've struggled enough with certain errors you should be able to catch and fix them whilst half asleep.[/QUOTE]

I'm looking at new areas of programming at the moment, so I suppose these new errors are just burrowing into my head slowly...