Generic Code Generator

Came across a useful code/password generator example for strong passwords at this site:

Obviex Password Example

I needed a random token generator for unit tests I wrote, so I extended it to do the following:

• Generate Alphabetical Code
• Generate Alphabetical Lower Case Code
• Generate Alphabetical Upper Case Code
• Generate Numerical Code

The code can be easily extended to include other combinations and variations.

   1: #region Usings

   2: using System;

   3: using System.Collections.Generic;

   4: using System.Linq;

   5: using System.Security.Cryptography;

   6: #endregion Usings

   7:  

   8: namespace AimKai.Core.Util

   9: {

  10:     /// <summary>

  11:     /// Random code generator

  12:     /// </summary>

  13:     public class RandomCodeGenerator

  14:     {

  15:         #region Constants

  16:  

  17:         /// <summary>

  18:         /// Default minimum code length

  19:         /// </summary>

  20:         private const int DefaultMinCodeLength = 8;

  21:  

  22:         /// <summary>

  23:         /// Default maximum code length

  24:         /// </summary>

  25:         private const int DefaultMaxCodeLength = 10;

  26:  

  27:         /// <summary>

  28:         /// Character set for lower case letters

  29:         /// </summary>

  30:         private const string CodeCharsLcase = "abcdefghijklmnopqrstuvwxyz";

  31:  

  32:         /// <summary>

  33:         /// Character set for upper case letters

  34:         /// </summary>

  35:         private const string CodeCharsUcase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

  36:  

  37:         /// <summary>

  38:         /// Character set for numerals

  39:         /// </summary>

  40:         private const string CodeNumerals = "0123456789";

  41:  

  42:         /// <summary>

  43:         /// Character set for specials

  44:         /// </summary>

  45:         private const string CodeCharsSpecial = "*$-+?_&=!%{}/";

  46:  

  47:         /// <summary>

  48:         /// Character set for non ambiguous lower cased letters

  49:         /// </summary>

  50:         private const string CodeCharsLcaseNonambig = "abcdefgijkmnopqrstwxyz";

  51:  

  52:         /// <summary>

  53:         /// Character set for non ambiguous upper cased letters

  54:         /// </summary>

  55:         private const string CodeCharsUcaseNonambig = "ABCDEFGHJKLMNPQRSTWXYZ";

  56:  

  57:         /// <summary>

  58:         /// Character set for non ambiguous letters

  59:         /// </summary>

  60:         private const string CodeNumeralsNonambig = "23456789";

  61:  

  62:         #endregion Constants

  63:  

  64:         #region Public Methods

  65:  

  66:         /// <summary>

  67:         /// Generates an alphanumeric random code between 8 and 10 characters

  68:         /// </summary>

  69:         /// <returns>Random code</returns>

  70:         public static string Generate ()

  71:         {

  72:             return Generate(DefaultMinCodeLength, DefaultMaxCodeLength, false, false, false, true, false, false);

  73:         }

  74:  

  75:         /// <summary>

  76:         /// Generates an alphanumeric random with passed minimum length and a maximum of 10 characters 

  77:         /// </summary>

  78:         /// <param name="minLength">Minimum length</param>

  79:         /// <returns>Random Code</returns>

  80:         public static string Generate(int minLength)

  81:         {

  82:             CheckParameters(minLength);

  83:             return Generate(minLength, minLength, false, false, false, true, false, false);

  84:         }

  85:  

  86:         /// <summary>

  87:         /// Generates an alphanumeric random with passed minimum and maximum lengths

  88:         /// </summary>

  89:         /// <param name="minLength">Minimum length</param>

  90:         /// <param name="maxLength">Maximum length</param>

  91:         /// <returns>Random Code</returns>

  92:         public static string Generate(int minLength, int maxLength)

  93:         {

  94:             CheckParameters(minLength, maxLength);

  95:             return Generate(minLength, maxLength, false, false, false, true, false, false);

  96:         }

  97:  

  98:         /// <summary>

  99:         /// Generate alphabetical code

 100:         /// </summary>

 101:         /// <returns>Random code</returns>

 102:         public static string GenerateAlphaOnly()

 103:         {

 104:             return Generate(DefaultMinCodeLength, DefaultMaxCodeLength, true, false, false, true, false, false);

 105:         }

 106:  

 107:         /// <summary>

 108:         /// Generate alphabetical code with passed length

 109:         /// </summary>

 110:         /// <param name="minLength">Minimum length</param>

 111:         /// <returns>Code</returns>

 112:         public static string GenerateAlphaOnly(int minLength)

 113:         {

 114:             CheckParameters(minLength);

 115:             return Generate(minLength, minLength, true, false, false, true, false, false);

 116:         }

 117:  

 118:         /// <summary>

 119:         /// Generate alphabetical code with passed length

 120:         /// </summary>

 121:         /// <param name="minLength">Minimum length</param>

 122:         /// <param name="maxLength">Maximum length</param>

 123:         /// <returns>Code</returns>

 124:         public static string GenerateAlphaOnly(int minLength, int maxLength)

 125:         {

 126:             CheckParameters(minLength, maxLength);

 127:             return Generate(minLength, maxLength, true, false, false, true, false, false);

 128:         }

 129:  

 130:         /// <summary>

 131:         /// Generate lower case alphabetical code

 132:         /// </summary>

 133:         /// <returns>Random code</returns>

 134:         public static string GenerateLowerCaseAlphaOnly()

 135:         {

 136:             return Generate(DefaultMinCodeLength, DefaultMaxCodeLength, true, false, false, true, true, false);

 137:         }

 138:  

 139:         /// <summary>

 140:         /// Generate lower case alphabetical code with passed minimum length

 141:         /// </summary>

 142:         /// <param name="minLength">Minimum length</param>

 143:         /// <returns>Code</returns>

 144:         public static string GenerateLowerCaseAlphaOnly(int minLength)

 145:         {

 146:             CheckParameters(minLength);

 147:             return Generate(minLength, minLength, true, false, false, true, true, false);

 148:         }

 149:  

 150:         /// <summary>

 151:         /// Generate lower case alphabetical code with passed minimum and maximum length 

 152:         /// </summary>

 153:         /// <param name="minLength">Minimum length</param>

 154:         /// <param name="maxLength">Maximum length</param>

 155:         /// <returns>Code</returns>

 156:         public static string GenerateLowerCaseAlphaOnly(int minLength, int maxLength)

 157:         {

 158:             CheckParameters(minLength, maxLength);

 159:             return Generate(minLength, maxLength, true, false, false, true, true, false);

 160:         }

 161:  

 162:         /// <summary>

 163:         /// Generate upper case alphabetical code

 164:         /// </summary>

 165:         /// <returns>Random code</returns>

 166:         public static string GenerateUpperCaseAlphaOnly()

 167:         {

 168:             return Generate(DefaultMinCodeLength, DefaultMaxCodeLength, true, false, false, true, false, true);

 169:         }

 170:  

 171:         /// <summary>

 172:         /// Generate lower case alphabetical code with passed minimum length

 173:         /// </summary>

 174:         /// <param name="minLength">Minimum length</param>

 175:         /// <returns>Code</returns>

 176:         public static string GenerateUpperCaseAlphaOnly(int minLength)

 177:         {

 178:             CheckParameters(minLength);

 179:             return Generate(minLength, minLength, true, false, false, true, false, true);

 180:         }

 181:  

 182:         /// <summary>

 183:         /// Generate lower case alphabetical code with passed minimum and maximum length 

 184:         /// </summary>

 185:         /// <param name="minLength">Minimum length</param>

 186:         /// <param name="maxLength">Maximum length</param>

 187:         /// <returns>Code</returns>

 188:         public static string GenerateUpperCaseAlphaOnly(int minLength, int maxLength)

 189:         {

 190:             CheckParameters(minLength, maxLength);

 191:             return Generate(minLength, maxLength, true, false, false, true, false, true);

 192:         }

 193:  

 194:         /// <summary>

 195:         /// Generate numerical code

 196:         /// </summary>

 197:         /// <returns>Random code</returns>

 198:         public static string GenerateNumericsOnly()

 199:         {

 200:             return Generate(DefaultMinCodeLength, DefaultMaxCodeLength, false, true, false, true,

 201:                              false, false);

 202:         }

 203:  

 204:         /// <summary>

 205:         /// Generate numerical code with minimum length

 206:         /// </summary>

 207:         /// <param name="minLength">Minimum length</param>

 208:         /// <returns>Random code</returns>

 209:         public static string GenerateNumericsOnly(int minLength)

 210:         {

 211:             CheckParameters(minLength);

 212:             return Generate(minLength, minLength, false, true, false, true,

 213:                              false, false);

 214:         }

 215:  

 216:         /// <summary>

 217:         /// Generate numerical code with maximum length

 218:         /// </summary>

 219:         /// <param name="minLength">Minimum length</param>

 220:         /// <param name="maxLength">Maximum length</param>

 221:         /// <returns>Random code</returns>

 222:         public static string GenerateNumericsOnly(int minLength, int maxLength)

 223:         {

 224:             CheckParameters(minLength, maxLength);

 225:             return Generate(minLength, maxLength, false, true, false, true, 

 226:                              false, false);

 227:         }

 228:  

 229:         /// <summary>

 230:         /// Generate strong password

 231:         /// </summary>

 232:         /// <returns>Strong password</returns>

 233:         public static string GenerateStrongPassword()

 234:         {

 235:             return Generate(DefaultMinCodeLength, DefaultMaxCodeLength, false, false, true, false,

 236:                             false, false);

 237:         }

 238:  

 239:         #endregion Public Methods

 240:  

 241:         /// <summary>

 242:         /// Generate code based on passed parameters

 243:         /// </summary>

 244:         /// <param name="minLength">Minimum length</param>

 245:         /// <param name="maxLength">Maximum length</param>

 246:         /// <param name="onlyLetters">Only letters</param>

 247:         /// <param name="onlyNumbers">Only numbers</param>

 248:         /// <param name="isStrong">Is strong password</param>

 249:         /// <param name="useAmbiguous">Use ambigous letters</param>

 250:         /// <param name="useLowerCaseOnly">Use lower case letters</param>

 251:         /// <param name="useUpperCaseOnly">Use upper case lettters</param>

 252:         /// <returns>Code</returns>

 253:         private static string Generate(int minLength, int maxLength, bool onlyLetters, bool onlyNumbers,

 254:             bool isStrong, bool useAmbiguous, bool useLowerCaseOnly, bool useUpperCaseOnly)

 255:         {           

 256:             //Determine what character groups 

 257:             var charGroups = DetermineCharGroups(isStrong, onlyLetters, useLowerCaseOnly, useAmbiguous, useUpperCaseOnly, onlyNumbers);

 258:  

 259:             // Use this array to track the number of unused characters in each

 260:             // character group.

 261:             var charsLeftInGroup = new int[charGroups.Length];

 262:  

 263:             // Initially, all characters in each group are not used.

 264:             for (var i = 0; i < charsLeftInGroup.Length; i++)

 265:                 charsLeftInGroup[i] = charGroups[i].Length;

 266:  

 267:             // Use this array to track (iterate through) unused character groups.

 268:             var leftGroupsOrder = new int[charGroups.Length];

 269:  

 270:             // Initially, all character groups are not used.

 271:             for (var i = 0; i < leftGroupsOrder.Length; i++)

 272:                 leftGroupsOrder[i] = i;

 273:  

 274:             // Generate random seed for random letter/numeral

 275:             var seed = GenerateSeed();

 276:  

 277:             // Now, this is real randomization.

 278:             var random = new Random(seed);

 279:  

 280:             // Allocate appropriate memory for the code.

 281:             var code = minLength < maxLength ? new char[random.Next(minLength, maxLength + 1)] : new char[minLength];

 282:  

 283:             // Index of the last non-processed group.

 284:             var lastLeftGroupsOrderIdx = leftGroupsOrder.Length - 1;

 285:  

 286:             // Generate code characters one at a time.

 287:             for (var i = 0; i < code.Length; i++)

 288:             {

 289:                 // If only one character group remained unprocessed, process it;

 290:                 // otherwise, pick a random character group from the unprocessed

 291:                 // group list. To allow a special character to appear in the

 292:                 // first position, increment the second parameter of the Next

 293:                 // function call by one, i.e. lastLeftGroupsOrderIdx + 1.

 294:                 int nextLeftGroupsOrderIdx;

 295:                 if (lastLeftGroupsOrderIdx == 0)

 296:                     nextLeftGroupsOrderIdx = 0;

 297:                 else

 298:                     nextLeftGroupsOrderIdx = random.Next(0,

 299:                                                          lastLeftGroupsOrderIdx);

 300:  

 301:                 // Get the actual index of the character group, from which we will

 302:                 // pick the next character.

 303:                 var nextGroupIdx = leftGroupsOrder[nextLeftGroupsOrderIdx];

 304:  

 305:                 // Get the index of the last unprocessed characters in this group.

 306:                 var lastCharIdx = charsLeftInGroup[nextGroupIdx] - 1;

 307:  

 308:                 // If only one unprocessed character is left, pick it; otherwise,

 309:                 // get a random character from the unused character list.

 310:                 var nextCharIdx = lastCharIdx == 0 ? 0 : random.Next(0, lastCharIdx + 1);

 311:  

 312:                 // Add this character to the code.

 313:                 code[i] = charGroups[nextGroupIdx][nextCharIdx];

 314:  

 315:                 // If we processed the last character in this group, start over.

 316:                 if (lastCharIdx == 0)

 317:                     charsLeftInGroup[nextGroupIdx] =

 318:                                               charGroups[nextGroupIdx].Length;

 319:                 // There are more unprocessed characters left.

 320:                 else

 321:                 {

 322:                     // Swap processed character with the last unprocessed character

 323:                     // so that we don't pick it until we process all characters in

 324:                     // this group.

 325:                     if (lastCharIdx != nextCharIdx)

 326:                     {

 327:                         var temp = charGroups[nextGroupIdx][lastCharIdx];

 328:                         charGroups[nextGroupIdx][lastCharIdx] =

 329:                                     charGroups[nextGroupIdx][nextCharIdx];

 330:                         charGroups[nextGroupIdx][nextCharIdx] = temp;

 331:                     }

 332:                     // Decrement the number of unprocessed characters in

 333:                     // this group.

 334:                     charsLeftInGroup[nextGroupIdx]--;

 335:                 }

 336:  

 337:                 // If we processed the last group, start all over.

 338:                 if (lastLeftGroupsOrderIdx == 0)

 339:                     lastLeftGroupsOrderIdx = leftGroupsOrder.Length - 1;

 340:                 // There are more unprocessed groups left.

 341:                 else

 342:                 {

 343:                     // Swap processed group with the last unprocessed group

 344:                     // so that we don't pick it until we process all groups.

 345:                     if (lastLeftGroupsOrderIdx != nextLeftGroupsOrderIdx)

 346:                     {

 347:                         var temp = leftGroupsOrder[lastLeftGroupsOrderIdx];

 348:                         leftGroupsOrder[lastLeftGroupsOrderIdx] =

 349:                                     leftGroupsOrder[nextLeftGroupsOrderIdx];

 350:                         leftGroupsOrder[nextLeftGroupsOrderIdx] = temp;

 351:                     }

 352:                     // Decrement the number of unprocessed groups.

 353:                     lastLeftGroupsOrderIdx--;

 354:                 }

 355:             }

 356:  

 357:             return new string(code);

 358:         }

 359:  

 360:         /// <summary>

 361:         /// Generate seed

 362:         /// </summary>

 363:         /// <returns>Seed</returns>

 364:         private static int GenerateSeed()

 365:         {

 366:             var randomBytes = new byte[4];

 367:             var rng = new RNGCryptoServiceProvider();

 368:             rng.GetBytes(randomBytes);

 369:  

 370:             // Convert 4 bytes into a 32-bit integer value.

 371:             return (randomBytes[0] & 0x7f) << 24 |

 372:                    randomBytes[1] << 16 |

 373:                    randomBytes[2] << 8 |

 374:                    randomBytes[3];

 375:         }

 376:  

 377:         /// <summary>

 378:         /// Determine character groups

 379:         /// </summary>

 380:         /// <param name="isStrong">Is strong password</param>

 381:         /// <param name="onlyLetters">Only letters</param>

 382:         /// <param name="useLowerCaseOnly">Lower case letters</param>

 383:         /// <param name="useAmbiguous">Ambiguous</param>

 384:         /// <param name="useUpperCaseOnly">Upper case letters</param>

 385:         /// <param name="onlyNumbers">Only numbers</param>

 386:         /// <returns>Character set</returns>

 387:         private static char[][] DetermineCharGroups(bool isStrong, bool onlyLetters, bool useLowerCaseOnly, bool useAmbiguous, bool useUpperCaseOnly, bool onlyNumbers)

 388:         {

 389:             IList<char[]> charGroups = new List<char[]>();

 390:  

 391:             if (isStrong)

 392:             {

 393:                 charGroups.Add(CodeCharsLcaseNonambig.ToCharArray());

 394:                 charGroups.Add(CodeNumeralsNonambig.ToCharArray());

 395:                 charGroups.Add(CodeCharsUcaseNonambig.ToCharArray());

 396:                 charGroups.Add(CodeCharsSpecial.ToCharArray());

 397:             }

 398:             else if ((onlyLetters) && (useLowerCaseOnly) && (!useAmbiguous))

 399:             {

 400:                 charGroups.Add(CodeCharsLcaseNonambig.ToCharArray());

 401:             }

 402:             else if ((onlyLetters) && (useLowerCaseOnly))

 403:             {

 404:                 charGroups.Add(CodeCharsLcase.ToCharArray());

 405:             }

 406:             else if ((onlyLetters) && (useUpperCaseOnly) && (!useAmbiguous))

 407:             {

 408:                 charGroups.Add(CodeCharsUcaseNonambig.ToCharArray());

 409:             }

 410:             else if ((onlyLetters) && (useUpperCaseOnly))

 411:             {

 412:                 charGroups.Add(CodeCharsUcase.ToCharArray());

 413:             }

 414:             else if (onlyLetters)

 415:             {

 416:                 charGroups.Add(CodeCharsLcase.ToCharArray());

 417:                 charGroups.Add(CodeCharsUcase.ToCharArray());

 418:             }

 419:             else if ((onlyNumbers) && (!useAmbiguous))

 420:             {

 421:                 charGroups.Add(CodeNumeralsNonambig.ToCharArray());

 422:             }

 423:             else if (onlyNumbers)

 424:             {

 425:                 charGroups.Add(CodeNumerals.ToCharArray());

 426:             }

 427:             else if (!useAmbiguous)

 428:             {

 429:                 charGroups.Add(CodeCharsLcaseNonambig.ToCharArray());

 430:                 charGroups.Add(CodeCharsUcaseNonambig.ToCharArray());

 431:                 charGroups.Add(CodeNumeralsNonambig.ToCharArray());                

 432:             }

 433:             else

 434:             {

 435:                 charGroups.Add(CodeCharsLcase.ToCharArray());

 436:                 charGroups.Add(CodeCharsUcase.ToCharArray());

 437:                 charGroups.Add(CodeNumerals.ToCharArray());                

 438:             }

 439:  

 440:             return charGroups.ToArray();

 441:  

 442:         }

 443:  

 444:         /// <summary>

 445:         /// Check parameters for minimum length

 446:         /// </summary>

 447:         /// <param name="minimumLength">Minimum length</param>

 448:         private static void CheckParameters(int minimumLength)

 449:         {

 450:             if (minimumLength <= 0)

 451:                 throw new Exception(string.Format("Must have a positive minimum length. Length passed was '{0}'",,

 452:                                         minimumLength));

 453:         }

 454:  

 455:         /// <summary>

 456:         /// Check parameters for maximum length

 457:         /// </summary>

 458:         /// <param name="minimumLength">Minimum length</param>

 459:         /// <param name="maximumLength">Maximum length</param>

 460:         private static void CheckParameters(int minimumLength, int maximumLength)

 461:         {

 462:             CheckParameters(minimumLength);

 463:  

 464:             if (maximumLength<= minimumLength)

 465:                 throw new Exception(string.Format("Must have a maximum length the same or longer than the minimum length. Maximum length '{0}' and Minimum Length '{1}'.",

 466:                     minimumLength, maximumLength));                    

 467:         }

 468:     }

 469: }