Question

Currently my program generates random 8 character strings made from numbers.

See below

public static string GenerateNewCode()
    {
        string newCode = String.Empty;
        int seed = unchecked(DateTime.Now.Ticks.GetHashCode());
        Random random = new Random(seed);

        // keep going until we find a unique code       
        do
        {
            newCode = random.Next(0, 9999).ToString("0000")
                    + random.Next(0, 9999).ToString("0000");
        }
        while (!ConsumerCode.isUnique(newCode));

        // return
        return newCode;
    }

However, I want to be able to create random codes of 8, 9, 10, 11 and 12 numbers.

Not sure the most efficient way of doing this.

My idea was to create a random number between 0 – 9 and then do this X amount of times based on the length of code required.

There must be an easy/more efficient way to doing this …..

Answer 1

internal class Program {
    private static void Main(string[] args) {
        Console.WriteLine(GetNumber(7));
        Console.WriteLine(GetNumber(8));
        Console.WriteLine(GetNumber(12));
        Console.WriteLine(GetNumber(500));
    }

    public static string GetNumber(int length) {
        return string.Concat(RandomDigits().Take(length));
    }

    public static IEnumerable<int> RandomDigits() {
        var rng = new Random(System.Environment.TickCount);
        while (true) yield return rng.Next(10);
    }
}

or

internal class Program {
    private static void Main(string[] args) {
        Console.WriteLine(GetNumber(12));
    }

    public static string GetNumber(int length) {
        var rng = new Random(Environment.TickCount);
        return string.Concat(Enumerable.Range(0, length).Select((index) => rng.Next(10).ToString()));
    }
}

Easy? yes. Most efficient? maybe not.