我如何在c#中生成一个随机的8个字符的字母数字字符串?


当前回答

下面是Eric J的解决方案的一个变体,即加密声音,用于WinRT (Windows商店应用程序):

public static string GenerateRandomString(int length)
{
    var chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
    var result = new StringBuilder(length);
    for (int i = 0; i < length; ++i)
    {
        result.Append(CryptographicBuffer.GenerateRandomNumber() % chars.Length);
    }
    return result.ToString();
}

如果性能很重要(特别是当长度很高时):

public static string GenerateRandomString(int length)
{
    var chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
    var result = new System.Text.StringBuilder(length);
    var bytes = CryptographicBuffer.GenerateRandom((uint)length * 4).ToArray();
    for (int i = 0; i < bytes.Length; i += 4)
    {
        result.Append(BitConverter.ToUInt32(bytes, i) % chars.Length);
    }
    return result.ToString();
}

其他回答

在这个线程中只是一些不同答案的性能比较:

方法与设置

// what's available
public static string possibleChars = "abcdefghijklmnopqrstuvwxyz";
// optimized (?) what's available
public static char[] possibleCharsArray = possibleChars.ToCharArray();
// optimized (precalculated) count
public static int possibleCharsAvailable = possibleChars.Length;
// shared randomization thingy
public static Random random = new Random();


// http://stackoverflow.com/a/1344242/1037948
public string LinqIsTheNewBlack(int num) {
    return new string(
    Enumerable.Repeat(possibleCharsArray, num)
              .Select(s => s[random.Next(s.Length)])
              .ToArray());
}

// http://stackoverflow.com/a/1344258/1037948
public string ForLoop(int num) {
    var result = new char[num];
    while(num-- > 0) {
        result[num] = possibleCharsArray[random.Next(possibleCharsAvailable)];
    }
    return new string(result);
}

public string ForLoopNonOptimized(int num) {
    var result = new char[num];
    while(num-- > 0) {
        result[num] = possibleChars[random.Next(possibleChars.Length)];
    }
    return new string(result);
}

public string Repeat(int num) {
    return new string(new char[num].Select(o => possibleCharsArray[random.Next(possibleCharsAvailable)]).ToArray());
}

// http://stackoverflow.com/a/1518495/1037948
public string GenerateRandomString(int num) {
  var rBytes = new byte[num];
  random.NextBytes(rBytes);
  var rName = new char[num];
  while(num-- > 0)
    rName[num] = possibleCharsArray[rBytes[num] % possibleCharsAvailable];
  return new string(rName);
}

//SecureFastRandom - or SolidSwiftRandom
static string GenerateRandomString(int Length) //Configurable output string length
{
    byte[] rBytes = new byte[Length]; 
    char[] rName = new char[Length];
    SolidSwiftRandom.GetNextBytesWithMax(rBytes, biasZone);
    for (var i = 0; i < Length; i++)
    {
        rName[i] = charSet[rBytes[i] % charSet.Length];
    }
    return new string(rName);
}

结果

在LinqPad中测试。对于长度为10的字符串,生成:

from Linq = chdgmevhcy [10] from Loop = gtnoaryhxr [10] from Select = rsndbztyby [10] from GenerateRandomString = owyefjjakj [10] from securefastrrandom = VzougLYHYP [10] from securefastrrandom - nocache = oVQXNGmO1S [10]

性能数据会有细微的变化,偶尔NonOptimized会更快,有时ForLoop和GenerateRandomString会切换谁领先。

LinqIsTheNewBlack (10000x) = 96762 ticks elapsed (9.6762 ms) ForLoop (10000x) = 28970滴答流逝(2.897毫秒) ForLoopNonOptimized (10000x) = 33336滴答流逝(3.3336毫秒) 重复(10000x) = 78547滴答流逝(7.8547毫秒) GenerateRandomString (10000x) = 27416 tick elapsed (2.7416 ms) securefastrrandom (10000x) = 13176滴答流逝(5ms)最低[不同的机器] securefastrrandom - nocache (10000x) = 39541 ticks elapsed (17ms) low[不同的机器]

我不知道这在密码学上听起来如何,但它比迄今为止(在我看来)更复杂的解决方案更具可读性和简练性,而且它应该比系统更“随机”。Random-based解决方案。

return alphabet
    .OrderBy(c => Guid.NewGuid())
    .Take(strLength)
    .Aggregate(
        new StringBuilder(),
        (builder, c) => builder.Append(c))
    .ToString();

我不知道我认为这个版本还是下一个版本“更漂亮”,但它们给出了完全相同的结果:

return new string(alphabet
    .OrderBy(o => Guid.NewGuid())
    .Take(strLength)
    .ToArray());

当然,它并没有针对速度进行优化,所以如果每秒生成数百万个随机字符串是关键任务,请尝试另一个!

注意:此解决方案不允许字母中符号的重复,并且字母必须等于或大于输出字符串的大小,使得这种方法在某些情况下不太可取,这完全取决于您的用例。

这里有一个机制来生成一个随机的字母-数字字符串(我用它来生成密码和测试数据),而不定义字母和数字,

CleanupBase64将删除字符串中必要的部分,并继续递归地添加随机的字母-数字字母。

        public static string GenerateRandomString(int length)
        {
            var numArray = new byte[length];
            new RNGCryptoServiceProvider().GetBytes(numArray);
            return CleanUpBase64String(Convert.ToBase64String(numArray), length);
        }

        private static string CleanUpBase64String(string input, int maxLength)
        {
            input = input.Replace("-", "");
            input = input.Replace("=", "");
            input = input.Replace("/", "");
            input = input.Replace("+", "");
            input = input.Replace(" ", "");
            while (input.Length < maxLength)
                input = input + GenerateRandomString(maxLength);
            return input.Length <= maxLength ?
                input.ToUpper() : //In my case I want capital letters
                input.ToUpper().Substring(0, maxLength);
        }

我听说LINQ是新的黑色,所以下面是我使用LINQ的尝试:

private static Random random = new Random();

public static string RandomString(int length)
{
    const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    return new string(Enumerable.Repeat(chars, length)
        .Select(s => s[random.Next(s.Length)]).ToArray());
}

(注意:Random类的使用使得它不适用于任何与安全性相关的事情,比如创建密码或令牌。如果你需要强随机数生成器,请使用RNGCryptoServiceProvider类。)

最简单和最灵活的加密安全解决方案(。NET Core 3.0+):

如果你使用的是。net Core 3.0或更高版本,你可以在RandomNumberGenerator类上使用新的静态GetInt32方法(这是加密安全的)来为给定的字符集生成随机索引,并以这种方式很容易地填充结果。

这种方法比这个答案中提出的方法要简单得多;它还提供了完全的灵活性,因为你可以传入任何你想要的字符集。

public static string GenerateRandomString(int length, IEnumerable<char> charSet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")
{
    var charArray = charSet.Distinct().ToArray();
    char[] result = new char[length];
    for (int i = 0; i < length; i++)
        result[i] = charArray[RandomNumberGenerator.GetInt32(charArray.Length)];
    return new string(result);
}

用法:

string randomAlphanumericString = GenerateRandomString(length: 10);