如何在C＃中生成随机的8个字符的字母数字字符串？
我听说LINQ是新的黑色，所以这是我尝试使用LINQ：
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：使用Random类使其不适用于任何与安全相关的内容，例如创建密码或令牌。如果需要强大的随机数生成器，请使用RNGCryptoServiceProvider类。）
Eric J.编写的代码非常草率（很明显它是从6年前开始的......他今天可能不会编写代码），甚至还有一些问题。
与提供的一些替代方案不同，这个方案是加密声音。
不真实......密码存在偏差（如评论中所述），bcdefgh比其他人更可能（a不是因为GetNonZeroBytes不生成值为零的字节，所以a的偏见是由它平衡的，所以它不是真正的加密声音。
这应该纠正所有问题。
public static string GetUniqueKey(int size = 6, string chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890")
{
using (var crypto = new RNGCryptoServiceProvider())
{
var data = new byte[size];
// If chars.Length isn't a power of 2 then there is a bias if
// we simply use the modulus operator. The first characters of
// chars will be more probable than the last ones.
// buffer used if we encounter an unusable random byte. We will
// regenerate it in this buffer
byte[] smallBuffer = null;
// Maximum random number that can be used without introducing a
// bias
int maxRandom = byte.MaxValue - ((byte.MaxValue + 1) % chars.Length);
crypto.GetBytes(data);
var result = new char[size];
for (int i = 0; i < size; i++)
{
byte v = data[i];
while (v > maxRandom)
{
if (smallBuffer == null)
{
smallBuffer = new byte[1];
}
crypto.GetBytes(smallBuffer);
v = smallBuffer[0];
}
result[i] = chars[v % chars.Length];
}
return new string(result);
}
}
另一个选择可能是使用Linq并将随机字符聚合到字符串构建器中。
var chars = "abcdefghijklmnopqrstuvwxyz123456789".ToArray();
string pw = Enumerable.Range(0, passwordLength)
.Aggregate(
new StringBuilder(),
(sb, n) => sb.Append((chars[random.Next(chars.Length)])),
sb => sb.ToString());
我们也使用自定义字符串随机，但我们实现的是字符串的帮助器，因此它提供了一些灵活性......
public static string Random(this string chars, int length = 8)
{
var randomString = new StringBuilder();
var random = new Random();
for (int i = 0; i < length; i++)
randomString.Append(chars[random.Next(chars.Length)]);
return randomString.ToString();
}
用法
var random = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".Random();
要么
var random = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".Random(16);
问题：为什么我要浪费时间使用Enumerable.Range而不是输入"ABCDEFGHJKLMNOPQRSTUVWXYZ0123456789"？
using System;
using System.Collections.Generic;
using System.Linq;
public class Test
{
public static void Main()
{
var randomCharacters = GetRandomCharacters(8, true);
Console.WriteLine(new string(randomCharacters.ToArray()));
}
private static List<char> getAvailableRandomCharacters(bool includeLowerCase)
{
var integers = Enumerable.Empty<int>();
integers = integers.Concat(Enumerable.Range('A', 26));
integers = integers.Concat(Enumerable.Range('0', 10));
if ( includeLowerCase )
integers = integers.Concat(Enumerable.Range('a', 26));
return integers.Select(i => (char)i).ToList();
}
public static IEnumerable<char> GetRandomCharacters(int count, bool includeLowerCase)
{
var characters = getAvailableRandomCharacters(includeLowerCase);
var random = new Random();
var result = Enumerable.Range(0, count)
.Select(_ => characters[random.Next(characters.Count)]);
return result;
}
}
答：魔术弦是不好的。是否有人注意到我的字符串顶部没有“I”？我母亲教我不要因为这个原因而使用魔法弦......
注： 1：正如许多其他像@dtb所说的那样，如果你需要加密安全性，请不要使用System.Random ...
注： 2：这个答案不是最有效或最短的，但我希望空间能够将答案与问题分开。我的回答的目的更多是警告魔法字符串，而不是提供一个奇特的创新答案。
我简单的一行代码对我有用:)
string random = string.Join("", Guid.NewGuid().ToString("n").Take(8).Select(o => o));
Response.Write(random.ToUpper());
Response.Write(random.ToLower());
为此扩展任何长度的字符串
public static string RandomString(int length)
{
//length = length < 0 ? length * -1 : length;
var str = "";
do
{
str += Guid.NewGuid().ToString().Replace("-", "");
}
while (length > str.Length);
return str.Substring(0, length);
}
DTB解决方案的略微清洁版本。
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
var random = new Random();
var list = Enumerable.Repeat(0, 8).Select(x=>chars[random.Next(chars.Length)]);
return string.Join("", list);
您的风格偏好可能会有所不
在回顾了其他答案并考虑了CodeInChaos的评论后，CodeInChaos仍然偏向于（虽然更少）答案，我认为需要最终的终极剪切和粘贴解决方案。所以在更新我的答案时，我决定全力以赴。
有关此代码的最新版本，请访问Bitbucket上的新Hg存储库：https://bitbucket.org/merarischroeder/secureswiftrandom。我建议您复制并粘贴以下代码：https://bitbucket.org/merarischroeder/secureswiftrandom/src/6c14b874f34a3f6576b0213379ecdf0ffc7496ea/Code/Alivate.SolidSwiftRandom/SolidSwiftRandom.cs?at=default&fileviewer=file-view-default（确保单击Raw按钮以便更容易复制并确保您拥有最新版本，我认为此链接转到特定版本的代码，而不是最新版本）。
更新的说明：
结束问题的解决方案：
static char[] charSet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".ToCharArray();
static int byteSize = 256; //Labelling convenience
static int biasZone = byteSize - (byteSize % charSet.Length);
public string GenerateRandomString(int Length) //Configurable output string length
{
byte[] rBytes = new byte[Length]; //Do as much before and after lock as possible
char[] rName = new char[Length];
SecureFastRandom.GetNextBytesMax(rBytes, biasZone);
for (var i = 0; i < Length; i++)
{
rName[i] = charSet[rBytes[i] % charSet.Length];
}
return new string(rName);
}
但是你需要我新的（未经测试的）课程：
/// <summary>
/// My benchmarking showed that for RNGCryptoServiceProvider:
/// 1. There is negligable benefit of sharing RNGCryptoServiceProvider object reference
/// 2. Initial GetBytes takes 2ms, and an initial read of 1MB takes 3ms (starting to rise, but still negligable)
/// 2. Cached is ~1000x faster for single byte at a time - taking 9ms over 1MB vs 989ms for uncached
/// </summary>
class SecureFastRandom
{
static byte[] byteCache = new byte[1000000]; //My benchmark showed that an initial read takes 2ms, and an initial read of this size takes 3ms (starting to raise)
static int lastPosition = 0;
static int remaining = 0;
/// <summary>
/// Static direct uncached access to the RNGCryptoServiceProvider GetBytes function
/// </summary>
/// <param name="buffer"></param>
public static void DirectGetBytes(byte[] buffer)
{
using (var r = new RNGCryptoServiceProvider())
{
r.GetBytes(buffer);
}
}
/// <summary>
/// Main expected method to be called by user. Underlying random data is cached from RNGCryptoServiceProvider for best performance
/// </summary>
/// <param name="buffer"></param>
public static void GetBytes(byte[] buffer)
{
if (buffer.Length > byteCache.Length)
{
DirectGetBytes(buffer);
return;
}
lock (byteCache)
{
if (buffer.Length > remaining)
{
DirectGetBytes(byteCache);
lastPosition = 0;
remaining = byteCache.Length;
}
Buffer.BlockCopy(byteCache, lastPosition, buffer, 0, buffer.Length);
lastPosition += buffer.Length;
remaining -= buffer.Length;
}
}
/// <summary>
/// Return a single byte from the cache of random data.
/// </summary>
/// <returns></returns>
public static byte GetByte()
{
lock (byteCache)
{
return UnsafeGetByte();
}
}
/// <summary>
/// Shared with public GetByte and GetBytesWithMax, and not locked to reduce lock/unlocking in loops. Must be called within lock of byteCache.
/// </summary>
/// <returns></returns>
static byte UnsafeGetByte()
{
if (1 > remaining)
{
DirectGetBytes(byteCache);
lastPosition = 0;
remaining = byteCache.Length;
}
lastPosition++;
remaining--;
return byteCache[lastPosition - 1];
}
/// <summary>
/// Rejects bytes which are equal to or greater than max. This is useful for ensuring there is no bias when you are modulating with a non power of 2 number.
/// </summary>
/// <param name="buffer"></param>
/// <param name="max"></param>
public static void GetBytesWithMax(byte[] buffer, byte max)
{
if (buffer.Length > byteCache.Length / 2) //No point caching for larger sizes
{
DirectGetBytes(buffer);
lock (byteCache)
{
UnsafeCheckBytesMax(buffer, max);
}
}
else
{
lock (byteCache)
{
if (buffer.Length > remaining) //Recache if not enough remaining, discarding remaining - too much work to join two blocks
DirectGetBytes(byteCache);
Buffer.BlockCopy(byteCache, lastPosition, buffer, 0, buffer.Length);
lastPosition += buffer.Length;
remaining -= buffer.Length;
UnsafeCheckBytesMax(buffer, max);
}
}
}
/// <summary>
/// Checks buffer for bytes equal and above max. Must be called within lock of byteCache.
/// </summary>
/// <param name="buffer"></param>
/// <param name="max"></param>
static void UnsafeCheckBytesMax(byte[] buffer, byte max)
{
for (int i = 0; i < buffer.Length; i++)
{
while (buffer[i] >= max)
buffer[i] = UnsafeGetByte(); //Replace all bytes which are equal or above max
}
}
}
对于历史 - 我这个答案的旧解决方案，使用Random对象：
private static char[] charSet =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".ToCharArray();
static rGen = new Random(); //Must share, because the clock seed only has Ticks (~10ms) resolution, yet lock has only 20-50ns delay.
static int byteSize = 256; //Labelling convenience
static int biasZone = byteSize - (byteSize % charSet.Length);
static bool SlightlyMoreSecurityNeeded = true; //Configuration - needs to be true, if more security is desired and if charSet.Length is not divisible by 2^X.
public string GenerateRandomString(int Length) //Configurable output string length
{
byte[] rBytes = new byte[Length]; //Do as much before and after lock as possible
char[] rName = new char[Length];
lock (rGen) //~20-50ns
{
rGen.NextBytes(rBytes);
for (int i = 0; i < Length; i++)
{
while (SlightlyMoreSecurityNeeded && rBytes[i] >= biasZone) //Secure against 1/5 increased bias of index[0-7] values against others. Note: Must exclude where it == biasZone (that is >=), otherwise there's still a bias on index 0.
rBytes[i] = rGen.NextByte();
rName[i] = charSet[rBytes[i] % charSet.Length];
}
}
return new string(rName);
}
性能：
还可以看看：
这些链接是另一种方法。缓冲可以添加到这个新的代码库中，但最重要的是探索消除偏差的不同方法，并对速度和优缺点进行基准测试。
可怕，我知道，但我无法自拔：
namespace ConsoleApplication2
{
using System;
using System.Text.RegularExpressions;
class Program
{
static void Main(string[] args)
{
Random adomRng = new Random();
string rndString = string.Empty;
char c;
for (int i = 0; i < 8; i++)
{
while (!Regex.IsMatch((c=Convert.ToChar(adomRng.Next(48,128))).ToString(), "[A-Za-z0-9]"));
rndString += c;
}
Console.WriteLine(rndString + Environment.NewLine);
}
}
}
我正在寻找一个更具体的答案，我想控制随机字符串的格式，并发现了这篇文章。例如：车牌（车辆）具有特定格式（每个国家），我想创建随机车牌。 我决定为此编写自己的Random扩展方法。 （这是为了重用相同的Random对象，因为你可以在多线程场景中使用双倍）。我创建了一个要点（https://gist.github.com/SamVanhoutte/808845ca78b9c041e928），但也会复制扩展类：
void Main()
{
Random rnd = new Random();
rnd.GetString("1-###-000").Dump();
}
public static class RandomExtensions
{
public static string GetString(this Random random, string format)
{
// Based on http://stackoverflow.com/questions/1344221/how-can-i-generate-random-alphanumeric-strings-in-c
// Added logic to specify the format of the random string (# will be random string, 0 will be random numeric, other characters remain)
StringBuilder result = new StringBuilder();
for(int formatIndex = 0; formatIndex < format.Length ; formatIndex++)
{
switch(format.ToUpper()[formatIndex])
{
case '0': result.Append(getRandomNumeric(random)); break;
case '#': result.Append(getRandomCharacter(random)); break;
default : result.Append(format[formatIndex]); break;
}
}
return result.ToString();
}
private static char getRandomCharacter(Random random)
{
string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
return chars[random.Next(chars.Length)];
}
private static char getRandomNumeric(Random random)
{
string nums = "0123456789";
return nums[random.Next(nums.Length)];
}
}
public static string RandomString(int length)
{
const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var random = new Random();
return new string(Enumerable.Repeat(chars, length).Select(s => s[random.Next(s.Length)]).ToArray());
}
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
var stringChars = new char[8];
var random = new Random();
for (int i = 0; i < stringChars.Length; i++)
{
stringChars[i] = chars[random.Next(chars.Length)];
}
var finalString = new String(stringChars);
不像Linq解决方案那么优雅。
（注意：使用Random类使其不适用于任何与安全相关的内容，例如创建密码或令牌。如果需要强大的随机数生成器，请使用RNGCryptoServiceProvider类。）
尝试组合两个部分：唯一（序列，计数器或日期）和随机
public class RandomStringGenerator
{
public static string Gen()
{
return ConvertToBase(DateTime.UtcNow.ToFileTimeUtc()) + GenRandomStrings(5); //keep length fixed at least of one part
}
private static string GenRandomStrings(int strLen)
{
var result = string.Empty;
var Gen = new RNGCryptoServiceProvider();
var data = new byte[1];
while (result.Length < strLen)
{
Gen.GetNonZeroBytes(data);
int code = data[0];
if (code > 48 && code < 57 || // 0-9
code > 65 && code < 90 || // A-Z
code > 97 && code < 122 // a-z
)
{
result += Convert.ToChar(code);
}
}
return result;
}
private static string ConvertToBase(long num, int nbase = 36)
{
var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; //if you wish make algoritm more secure - change order of letter here
// check if we can convert to another base
if (nbase < 2 || nbase > chars.Length)
return null;
int r;
var newNumber = string.Empty;
// in r we have the offset of the char that was converted to the new base
while (num >= nbase)
{
r = (int) (num % nbase);
newNumber = chars[r] + newNumber;
num = num / nbase;
}
// the last number to convert
newNumber = chars[(int)num] + newNumber;
return newNumber;
}
}
测试：
[Test]
public void Generator_Should_BeUnigue1()
{
//Given
var loop = Enumerable.Range(0, 1000);
//When
var str = loop.Select(x=> RandomStringGenerator.Gen());
//Then
var distinct = str.Distinct();
Assert.AreEqual(loop.Count(),distinct.Count()); // Or Assert.IsTrue(distinct.Count() < 0.95 * loop.Count())
}
不使用Random的解决方案：
var chars = Enumerable.Repeat("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789", 8);
var randomStr = new string(chars.SelectMany(str => str)
.OrderBy(c => Guid.NewGuid())
.Take(8).ToArray());
以下是针对WinRT（Windows应用商店应用）的Eric J解决方案的变体，即加密声音：
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();
}
现在是单线风味。
private string RandomName
{
get
{
return new string(
Enumerable.Repeat("ABCDEFGHIJKLMNOPQRSTUVWXYZ", 13)
.Select(s =>
{
var cryptoResult = new byte[4];
using (var cryptoProvider = new RNGCryptoServiceProvider())
cryptoProvider.GetBytes(cryptoResult);
return s[new Random(BitConverter.ToInt32(cryptoResult, 0)).Next(s.Length)];
})
.ToArray());
}
}
我知道这不是最好的方法。但你可以试试这个。
string str = Path.GetRandomFileName(); //This method returns a random file name of 11 characters
str = str.Replace(".","");
Console.WriteLine("Random string: " + str);
我不知道这是多么密码，但它比迄今为止更复杂的解决方案（imo）更具可读性和简洁性，并且它应该比基于System.Random的解决方案更“随机”。
return alphabet
.OrderBy(c => Guid.NewGuid())
.Take(strLength)
.Aggregate(
new StringBuilder(),
(builder, c) => builder.Append(c))
.ToString();
我无法决定我认为这个版本或下一个版本是否“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，因此如果每秒产生数百万个随机字符串至关重要，那么请尝试另一个！
注意：此解决方案不允许在字母表中重复符号，并且字母必须与输出字符串的大小相等或更大，这使得在某些情况下这种方法不太理想，这一切都取决于您的用例。
如果你的值不是完全随机的，但实际上可能取决于某些东西 - 你可以计算一个'somwthing'的md5或sha1哈希值，然后将其截断到你想要的任何长度。
你也可以生成并截断一个guid。
public static class StringHelper
{
private static readonly Random random = new Random();
private const int randomSymbolsDefaultCount = 8;
private const string availableChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
private static int randomSymbolsIndex = 0;
public static string GetRandomSymbols()
{
return GetRandomSymbols(randomSymbolsDefaultCount);
}
public static string GetRandomSymbols(int count)
{
var index = randomSymbolsIndex;
var result = new string(
Enumerable.Repeat(availableChars, count)
.Select(s => {
index += random.Next(s.Length);
if (index >= s.Length)
index -= s.Length;
return s[index];
})
.ToArray());
randomSymbolsIndex = index;
return result;
}
}
这是一种生成随机字母数字字符串（我使用它来生成密码和测试数据）而不定义字母和数字的机制，
CleanupBase64将删除字符串中的必要部分，并继续递归添加随机字母数字字母。
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);
}
很简单的解决方案它使用ASCII值，只在它们之间生成“随机”字符。
public static class UsernameTools
{
public static string GenerateRandomUsername(int length = 10)
{
Random random = new Random();
StringBuilder sbuilder = new StringBuilder();
for (int x = 0; x < length; ++x)
{
sbuilder.Append((char)random.Next(33, 126));
}
return sbuilder.ToString();
}
}
这个实现（通过谷歌找到）看起来很健康。
与提供的一些替代方案不同，这个方案是加密声音。
using System.Security.Cryptography;
using System.Text;
namespace UniqueKey
{
public class KeyGenerator
{
public static string GetUniqueKey(int size)
{
char[] chars =
"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".ToCharArray();
byte[] data = new byte[size];
using (RNGCryptoServiceProvider crypto = new RNGCryptoServiceProvider())
{
crypto.GetBytes(data);
}
StringBuilder result = new StringBuilder(size);
foreach (byte b in data)
{
result.Append(chars[b % (chars.Length)]);
}
return result.ToString();
}
}
}
从讨论替代品here中挑选出一个
你只需使用组件SRVTextToImage。并在下面写下代码来生成随机字符串。
CaptchaRandomImage c1 = new CaptchaRandomImage();
string text = c1.GetRandomString(8);
它主要用于实现Captcha。但在你的情况下它也有效。希望能帮助到你。
解决方案1 - 最大的“范围”，最灵活的长度
string get_unique_string(int string_length) {
using(var rng = new RNGCryptoServiceProvider()) {
var bit_count = (string_length * 6);
var byte_count = ((bit_count + 7) / 8); // rounded up
var bytes = new byte[byte_count];
rng.GetBytes(bytes);
return Convert.ToBase64String(bytes);
}
}
此解决方案比使用GUID具有更多的范围，因为GUID具有几个始终相同且因此不是随机的固定位，例如十六进制中的13个字符始终为“4” - 至少在版本6 GUID中。
此解决方案还允许您生成任意长度的字符串。
解决方案2 - 一行代码 - 最多22个字符
Convert.ToBase64String(Guid.NewGuid().ToByteArray()).Substring(0, 8);
只要解决方案1和字符串由于GUID中的固定位而没有相同的范围，就无法生成字符串，但在很多情况下，这将完成工作。
解决方案3 - 略少的代码
Guid.NewGuid().ToString("n").Substring(0, 8);
大部分时间都是为了历史目的。它使用稍微少一点的代码，虽然这是为了减少范围 - 因为它使用十六进制代替base64，与其他解决方案相比，它需要更多的字符来表示相同的范围。
这意味着更多的碰撞机会 - 使用100,000个迭代的8个字符串测试它会产生一个重复。
这是我从Dot Net Perls的Sam Allen示例中偷走的一个例子
如果只需要8个字符，则在System.IO命名空间中使用Path.GetRandomFileName（）。 Sam说使用“Path.GetRandomFileName方法有时候更好，因为它使用RNGCryptoServiceProvider来获得更好的随机性。但是，它只限于11个随机字符。”
GetRandomFileName始终返回一个12个字符的字符串，其句点为第9个字符。所以你需要去除句点（因为那不是随机的）然后从字符串中取出8个字符。实际上，你可以只取前8个字符而不用担心这段时间。
public string Get8CharacterRandomString()
{
string path = Path.GetRandomFileName();
path = path.Replace(".", ""); // Remove period.
return path.Substring(0, 8); // Return 8 character string
}
PS：谢谢Sam
我的代码的主要目标是：
第一个属性是通过将64位值模数为字母大小来实现的。对于小字母（例如来自问题的62个字符），这导致可忽略的偏差。第二和第三个属性是通过使用RNGCryptoServiceProvider而不是System.Random实现的。
using System;
using System.Security.Cryptography;
public static string GetRandomAlphanumericString(int length)
{
const string alphanumericCharacters =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
"abcdefghijklmnopqrstuvwxyz" +
"0123456789";
return GetRandomString(length, alphanumericCharacters);
}
public static string GetRandomString(int length, IEnumerable<char> characterSet)
{
if (length < 0)
throw new ArgumentException("length must not be negative", "length");
if (length > int.MaxValue / 8) // 250 million chars ought to be enough for anybody
throw new ArgumentException("length is too big", "length");
if (characterSet == null)
throw new ArgumentNullException("characterSet");
var characterArray = characterSet.Distinct().ToArray();
if (characterArray.Length == 0)
throw new ArgumentException("characterSet must not be empty", "characterSet");
var bytes = new byte[length * 8];
var result = new char[length];
using (var cryptoProvider = new RNGCryptoServiceProvider())
{
cryptoProvider.GetBytes(bytes);
}
for (int i = 0; i < length; i++)
{
ulong value = BitConverter.ToUInt64(bytes, i * 8);
result[i] = characterArray[value % (uint)characterArray.Length];
}
return new string(result);
}
最简单的：
public static string GetRandomAlphaNumeric()
{
return Path.GetRandomFileName().Replace(".", "").Substring(0, 8);
}
如果你对char数组进行硬编码并依赖System.Random，你可以获得更好的性能：
public static string GetRandomAlphaNumeric()
{
var chars = "abcdefghijklmnopqrstuvwxyz0123456789";
return new string(chars.Select(c => chars[random.Next(chars.Length)]).Take(8).ToArray());
}
如果你担心英文字母可以在某个时候改变而你可能会失去业务，那么你可以避免硬编码，但应该表现稍差（与Path.GetRandomFileName方法相当）
public static string GetRandomAlphaNumeric()
{
var chars = 'a'.To('z').Concat('0'.To('9')).ToList();
return new string(chars.Select(c => chars[random.Next(chars.Length)]).Take(8).ToArray());
}
public static IEnumerable<char> To(this char start, char end)
{
if (end < start)
throw new ArgumentOutOfRangeException("the end char should not be less than start char", innerException: null);
return Enumerable.Range(start, end - start + 1).Select(i => (char)i);
}
如果你可以在System.Random实例上使它们成为扩展方法，那么最后两种方法看起来会更好。
只是对这个帖子中各种答案的一些性能比较：
// 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);
}
在LinqPad中测试过。对于字符串大小10，生成：
- 来自Linq = chdgmevhcy [10]
- 来自Loop = gtnoaryhxr [10]
- 来自Select = rsndbztyby [10]
- 来自GenerateRandomString = owyefjjakj [10]
- 来自SecureFastRandom = VzougLYHYP [10]
- 来自SecureFastRandom-NoCache = oVQXNGmO1S [10]
性能数据往往略有不同，偶尔NonOptimized实际上更快，有时ForLoop和GenerateRandomString切换谁领先。
- LinqIsTheNewBlack（10000x）= 96762个刻度（9.6762毫秒）
- ForLoop（10000x）= 28970个刻度（2.897毫秒）
- ForLoopNonOptimized（10000x）= 33336个刻度已过去（3.3336毫秒）
- 重复（10000x）= 78547个刻度（7.8547毫秒）
- GenerateRandomString（10000x）=经过了27416个刻度（2.7416 ms）
- SecureFastRandom（10000x）= 13176个刻度（5ms）最低[不同的机器]
- SecureFastRandom-NoCache（10000x）= 39541个刻度（17ms）最低[不同的机器]
一行代码Membership.GeneratePassword()做的伎俩:)
这是一个相同的demo。