How to generate a random string, and specify the length you want, or better generate unique string on specification you want

Question

There is a library to generate Random numbers, so why isn\'t there a library for generation of random strings?

In other words how to generate a random string, and sp

Answer 1

How about

string.Join("", Enumerable.Repeat(0, 100).Select(n => (char)new Random().Next(127)));

or

var rand = new Random();
string.Join("", Enumerable.Repeat(0, 100).Select(n => (char)rand.Next(127)));

Answer 2

public  static String getAlphaNumericString(int n) {

        String AlphaNumericString = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "0123456789" + "abcdefghijklmnopqrstuvxyz";

        StringBuilder sb = new StringBuilder(n);

        for (int i = 0; i < n; i++) {

            // generate a random number between
            // 0 to AlphaNumericString variable length
            int index = (int) (AlphaNumericString.length() * Math.random());

            // add Character one by one in end of sb
            sb.append(AlphaNumericString.charAt(index));
        }

        return sb.toString();
    }

Answer 3

How about-

    static Random rd = new Random();
    internal static string CreateString(int stringLength)
    {
        const string allowedChars = "ABCDEFGHJKLMNOPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz0123456789!@$?_-";
        char[] chars = new char[stringLength];

        for (int i = 0; i < stringLength; i++)
        {
            chars[i] = allowedChars[rd.Next(0, allowedChars.Length)];
        }

        return new string(chars);
    }

Answer 4

Sometimes a random string can be useful in something like a unit test, if it was me I would add the AutoFixture nuget package and then do something like this. In my example I need a 121 character string...

        var fixture = new Fixture();
        var chars = fixture.CreateMany<char>(121).ToArray();
        var myString = new string(chars);

If this wasn't in a unit test then I'd create myself a nuget package and use Autofixture in that, or something else if I needed only certain character types.

Answer 5

I can't recall where I got this, so if you know who originally authored this, please help me give attribution.

private static void Main()
{
    const string AllowedChars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz#@$^*()";
    Random rng = new Random();

    foreach (string randomString in rng.NextStrings(AllowedChars, (15, 64), 25))
    {
        Console.WriteLine(randomString);
    }

    Console.ReadLine();
}

private static IEnumerable<string> NextStrings(
    this Random rnd,
    string allowedChars,
    (int Min, int Max)length,
    int count)
{
    ISet<string> usedRandomStrings = new HashSet<string>();
    (int min, int max) = length;
    char[] chars = new char[max];
    int setLength = allowedChars.Length;

    while (count-- > 0)
    {
        int stringLength = rnd.Next(min, max + 1);

        for (int i = 0; i < stringLength; ++i)
        {
            chars[i] = allowedChars[rnd.Next(setLength)];
        }

        string randomString = new string(chars, 0, stringLength);

        if (usedRandomStrings.Add(randomString))
        {
            yield return randomString;
        }
        else
        {
            count++;
        }
    }
}