Generate random string [duplicate]

Answer 1

You could save yourself the hassle and use Membership.GeneratePassword method. It is essentially doing what you require.

Usage:

int passwordLength = 5;
int alphaNumericalCharsAllowed = 2;
string random = Membership.GeneratePassword(passwordLength, alphaNumericalCharsAllowed);

For readability aswell you could wrap this in a helper method:

private string GenerateRandomString(int length, int alphaNumericalChars)
{
      return Membership.GeneratePassword(length, alphaNumericalChars);
}

Answer 2

Nothing special, but short. 32 and 127 are min and max range of chars you want to be generated.

public static string GetRandomString(int length)
{
    var r = new Random();
    return new String(Enumerable.Range(0, length).Select(n => (Char)(r.Next(32, 127))).ToArray());
}

Answer 3

http://msdn.microsoft.com/en-us/library/system.io.path.getrandomfilename.aspx

string randomName = Path.GetRandomFileName();
randomName = randomName.Replace(".", string.Empty);

// take substring...

Answer 4

Don't create a new instance of Random on each iteration - that's going to seed each instance with the current time in milliseconds, which obviously isn't likely to change between iterations.

Create a single instance of Random, and pass it into the method. I'd also advise you not to concatenate strings like that in a loop, or even to create that many strings. Additionally, if you use Random.Next(int, int) to make your life a lot easier.

Try this:

public char GenerateChar(Random rng)
{
    // 'Z' + 1 because the range is exclusive
    return (char) (rng.Next('A', 'Z' + 1));
}

public string GenerateString(Random rng, int length)
{ 
    char[] letters = new char[length];
    for (int i = 0; i < length; i++)
    {
        letters[i] = GenerateChar(rng);
    }
    return new string(letters);
}

private static readonly Random SingleRandom = new Random();

public string GenerateStringNotThreadSafe(int length)
{ 
    return GenerateString(SingleRandom, length);
}

Now it's worth being aware that Random isn't thread-safe, so if you've got multiple threads you shouldn't just have a single instance of Random in a static variable without locking. There are various ways around this - either create a subclass of Random which is thread-safe, or a set of static methods which do the same thing, or use thread-local variables to have one instance per thread.

I have a StaticRandom class as part of MiscUtil but these days I'm leaning towards the thread-local version and passing it down the chain where appropriate. One day I'll add that as another option to MiscUtil...

Answer 5

Try this out.

public string GetRandomString()
{
    int randomNumber = new Random().Next();
    string RandomString = string.Empty;
    for(int i = 0;i < randomNumber.ToString().Length;i++)
    {
        RandomString += ((char)Convert.ToUInt32(randomNumber.ToString()[i])).ToString();
    }
    return RandomString;
}

Answer 6

You should initialize your random variable outside the method:

public Random random = new Random();

public string GenerateChar()
    {
       return Convert.ToChar(Convert.ToInt32(Math.Floor(26 * random.NextDouble() + 65))).ToString();
    }

...