.NET Short Unique Identifier

Question

I need a unique identifier in .NET (cannot use GUID as it is too long for this case).

Do people think that the algorithm used here is a good candidate or do you have

Answer 1

I know it's quite far from posted date... :)

I have a generator which produces only 9 Hexa characters, eg: C9D6F7FF3, C9D6FB52C

public class SlimHexIdGenerator : IIdGenerator
{
    private readonly DateTime _baseDate = new DateTime(2016, 1, 1);
    private readonly IDictionary> _cache = new Dictionary>();

    public string NewId()
    {
        var now = DateTime.Now.ToString("HHmmssfff");
        var daysDiff = (DateTime.Today - _baseDate).Days;
        var current = long.Parse(string.Format("{0}{1}", daysDiff, now));
        return IdGeneratorHelper.NewId(_cache, current);
    }
}


static class IdGeneratorHelper
{
    public static string NewId(IDictionary> cache, long current)
    {
        if (cache.Any() && cache.Keys.Max() < current)
        {
            cache.Clear();
        }

        if (!cache.Any())
        {
            cache.Add(current, new List());
        }

        string secondPart;
        if (cache[current].Any())
        {
            var maxValue = cache[current].Max();
            cache[current].Add(maxValue + 1);
            secondPart = maxValue.ToString(CultureInfo.InvariantCulture);
        }
        else
        {
            cache[current].Add(0);
            secondPart = string.Empty;
        }

        var nextValueFormatted = string.Format("{0}{1}", current, secondPart);
        return UInt64.Parse(nextValueFormatted).ToString("X");
    }
}