CSharp – Random Password Generator

Sometimes it’s helpful to simply have a random password.

In this small group of code you can define what parameters to use, I have taken the liberty to remove some of the characters that are usually mistaken for a different character like an upper case I and the number 1.

private static int DEFAULT_MAX_PASSWORD_LENGTH = 10;
private static int DEFAULT_MIN_PASSWORD_LENGTH = 8;
private static string PASSWORD_CHARS_LCASE = "abcdefgijkmnopqrstwxyz";
private static string PASSWORD_CHARS_NUMERIC = "23456789";
private static string PASSWORD_CHARS_SPECIAL = "*$+?&!%";
private static string PASSWORD_CHARS_UCASE = "ABCDEFGHJKLMNPQRSTWXYZ";

Full Source Code

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Security.Cryptography;

namespace Project1
{
	public partial class Form1 : Form
	{
		public Form1()
		{
			InitializeComponent();
		}

		private void Form1_Load(object sender, EventArgs e)
		{
			MessageBox.Show(RandomPassword.Generate());
		}
	}

	public class RandomPassword
	{
		private static int DEFAULT_MAX_PASSWORD_LENGTH = 10;
		private static int DEFAULT_MIN_PASSWORD_LENGTH = 8;
		private static string PASSWORD_CHARS_LCASE = "abcdefgijkmnopqrstwxyz";
		private static string PASSWORD_CHARS_NUMERIC = "23456789";
		private static string PASSWORD_CHARS_SPECIAL = "*$+?&!%";
		private static string PASSWORD_CHARS_UCASE = "ABCDEFGHJKLMNPQRSTWXYZ";

		public static string Generate()
		{
			return Generate(DEFAULT_MIN_PASSWORD_LENGTH, DEFAULT_MAX_PASSWORD_LENGTH);
		}

		public static string Generate(int length)
		{
			return Generate(length, length);
		}

		public static string Generate(int minLength, int maxLength)
		{
			if (((minLength <= 0) || (maxLength <= 0)) || (minLength > maxLength))
			{
				return null;
			}
			char[][] chArray = new char[][] { PASSWORD_CHARS_LCASE.ToCharArray(), PASSWORD_CHARS_UCASE.ToCharArray(), PASSWORD_CHARS_NUMERIC.ToCharArray(), PASSWORD_CHARS_SPECIAL.ToCharArray() };
			int[] numArray = new int[chArray.Length];
			for (int i = 0; i < numArray.Length; i++)
			{
				numArray[i] = chArray[i].Length;
			}
			int[] numArray2 = new int[chArray.Length];
			for (int j = 0; j < numArray2.Length; j++)
			{
				numArray2[j] = j;
			}
			byte[] data = new byte[4];
			new RNGCryptoServiceProvider().GetBytes(data);
			int seed = ((((data[0] & 0x7f) << 0x18) | (data[1] << 0x10)) | (data[2] << 8)) | data[3];
			Random random = new Random(seed);
			char[] chArray2 = null;
			if (minLength < maxLength)
			{
				chArray2 = new char[random.Next(minLength, maxLength + 1)];
			}
			else
			{
				chArray2 = new char[minLength];
			}
			int maxValue = numArray2.Length - 1;
			for (int k = 0; k < chArray2.Length; k++)
			{
				int num4;
				int num6;
				if (maxValue == 0)
				{
					num6 = 0;
				}
				else
				{
					num6 = random.Next(0, maxValue);
				}
				int index = numArray2[num6];
				int num7 = numArray[index] - 1;
				if (num7 == 0)
				{
					num4 = 0;
				}
				else
				{
					num4 = random.Next(0, num7 + 1);
				}
				chArray2[k] = chArray[index][num4];
				if (num7 == 0)
				{
					numArray[index] = chArray[index].Length;
				}
				else
				{
					if (num7 != num4)
					{
						char ch = chArray[index][num7];
						chArray[index][num7] = chArray[index][num4];
						chArray[index][num4] = ch;
					}
					numArray[index]--;
				}
				if (maxValue == 0)
				{
					maxValue = numArray2.Length - 1;
				}
				else
				{
					if (maxValue != num6)
					{
						int num10 = numArray2[maxValue];
						numArray2[maxValue] = numArray2[num6];
						numArray2[num6] = num10;
					}
					maxValue--;
				}
			}
			return new string(chArray2);
		}
	}
}

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