Posts Tagged ‘Random’

A Simplistic Random String Generation Snippet

January 25th, 2010

This is just a little snippet that generates a random string, containing both upper and lower case characters and special chars, so there’s a range of 93 possible characters, taken from the UTF-8 character table. I thought I’d post it as the snippets I’ve seen after a quick search usually just generate strings with characters ranging from ‘A’ to ‘Z’, or do not work with properly initialized seeds.

Note that this method uses a static int field (seedCounter) when in comes to creating a random seed. This counter is incremented in a thread safe manner every time the method is being invoked. This simple trick is a simple workaround to the notoriously unreliable Random class, and effectively prevents double seeds (and thus: duplicate “random strings”) if the GetRandomString method is being invoked several times immediately. As an alternative, you could also use a static Random field, which would only have to be initialized once. My implementation has the smaller footprint (and integer variable), while a Random field would perform much better (currently, every invocation calculates a seed and creates a new Random instance). The better choice depends on the context I guess:


/// <summary>
/// A counter that is being incremented with every invocation of
/// <see cref="GetRandomString"/>.
/// </summary>
private static int seedCounter = (int)DateTime.Now.Ticks;

/// <summary>
/// Generates a random string of a given length, which consists
/// of characters taken from the UTF-8 table (0x21 - 0x7e).
/// </summary>
/// <param name="length">The length of the random string.</param>
/// <returns>Random characters.</returns>
public static string GetRandomString(int length)
  const int lower = 0x21;
  const int upper = 0x7e;

  StringBuilder builder = new StringBuilder();

  //increment thread-safe
  seedCounter = Interlocked.Increment(ref seedCounter);

  //create random with the seed (make sure it's not int.MinValue)
  Random rnd = new Random(seedCounter %int.MinValue);

  for (int i = 0; i < length; i++)
    builder.Append((char) rnd.Next(lower, upper));

  return builder.ToString();


Accordingly, invoking the method like this:

string random = GetRandomString(10);


…generates you a string comparable to this one: 2#,R`6>Cz{

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