ASP.NET Random Password Generator by Kevin Stewart copy paste www.codeproject.com

namespace WorkingCode.CodeProject.PwdGen
{
using System;
using System.Security.Cryptography;
using System.Text;

public class PasswordGenerator
{
public PasswordGenerator()
{
this.Minimum = DefaultMinimum;
this.Maximum = DefaultMaximum;
this.ConsecutiveCharacters = false;
this.RepeatCharacters = true;
this.ExcludeSymbols = false;
this.Exclusions = null;

rng = new RNGCryptoServiceProvider();
}

protected int GetCryptographicRandomNumber(int lBound, int uBound)
{
// Assumes lBound >= 0 && lBound < uBound // returns an int >= lBound and < uBound uint urndnum; byte[] rndnum = new Byte[4]; if (lBound == uBound-1) { // test for degenerate case where only lBound can be returned return lBound; } uint xcludeRndBase = (uint.MaxValue - (uint.MaxValue%(uint)(uBound-lBound))); do { rng.GetBytes(rndnum); urndnum = System.BitConverter.ToUInt32(rndnum,0); } while (urndnum >= xcludeRndBase);

return (int)(urndnum % (uBound-lBound)) + lBound;
}

protected char GetRandomCharacter()
{
int upperBound = pwdCharArray.GetUpperBound(0);

if ( true == this.ExcludeSymbols )
{
upperBound = PasswordGenerator.UBoundDigit;
}

int randomCharPosition = GetCryptographicRandomNumber(
pwdCharArray.GetLowerBound(0), upperBound);

char randomChar = pwdCharArray[randomCharPosition];

return randomChar;
}

public string Generate()
{
// Pick random length between minimum and maximum
int pwdLength = GetCryptographicRandomNumber(this.Minimum,
this.Maximum);

StringBuilder pwdBuffer = new StringBuilder();
pwdBuffer.Capacity = this.Maximum;

// Generate random characters
char lastCharacter, nextCharacter;

// Initial dummy character flag
lastCharacter = nextCharacter = '\n';

for ( int i = 0; i < pwdLength; i++ ) { nextCharacter = GetRandomCharacter(); if ( false == this.ConsecutiveCharacters ) { while ( lastCharacter == nextCharacter ) { nextCharacter = GetRandomCharacter(); } } if ( false == this.RepeatCharacters ) { string temp = pwdBuffer.ToString(); int duplicateIndex = temp.IndexOf(nextCharacter); while ( -1 != duplicateIndex ) { nextCharacter = GetRandomCharacter(); duplicateIndex = temp.IndexOf(nextCharacter); } } if ( ( null != this.Exclusions ) ) { while ( -1 != this.Exclusions.IndexOf(nextCharacter) ) { nextCharacter = GetRandomCharacter(); } } pwdBuffer.Append(nextCharacter); lastCharacter = nextCharacter; } if ( null != pwdBuffer ) { return pwdBuffer.ToString(); } else { return String.Empty; } } public string Exclusions { get { return this.exclusionSet; } set { this.exclusionSet = value; } } public int Minimum { get { return this.minSize; } set { this.minSize = value; if ( PasswordGenerator.DefaultMinimum > this.minSize )
{
this.minSize = PasswordGenerator.DefaultMinimum;
}
}
}

public int Maximum
{
get { return this.maxSize; }
set
{
this.maxSize = value;
if ( this.minSize >= this.maxSize )
{
this.maxSize = PasswordGenerator.DefaultMaximum;
}
}
}

public bool ExcludeSymbols
{
get { return this.hasSymbols; }
set { this.hasSymbols = value;}
}

public bool RepeatCharacters
{
get { return this.hasRepeating; }
set { this.hasRepeating = value;}
}

public bool ConsecutiveCharacters
{
get { return this.hasConsecutive; }
set { this.hasConsecutive = value;}
}

private const int DefaultMinimum = 6;
private const int DefaultMaximum = 10;
private const int UBoundDigit = 61;

private RNGCryptoServiceProvider rng;
private int minSize;
private int maxSize;
private bool hasRepeating;
private bool hasConsecutive;
private bool hasSymbols;
private string exclusionSet;
private char[] pwdCharArray = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789`~!@#$%^&*()-_=+[]{}\\|;:'\",<.>/?".ToCharArray();
}
}