Formatting Large Numbers with .NET

Question

I have a requirement to format large numbers like 4,316,000 as \"4.3m\".

How can I do this in C#?

Answer 1

public static class Program
{
    private static void Main(string[] args)
    {
        double[] numbers =
        {
            3000, 3300, 3333, 30000, 300000, 3000000, 3000003, 0.253, 0.0253, 0.00253, -0.253003
        };

        foreach (var num in numbers)
        {
            Console.WriteLine($"{num} ==> {num.Humanize()}");
        }

        Console.ReadKey();
    }

    public static string Humanize(this double number)
    {
        string[] suffix = {"f", "a", "p", "n", "μ", "m", string.Empty, "k", "M", "G", "T", "P", "E"};

        var absnum = Math.Abs(number);

        int mag;
        if (absnum < 1)
        {
            mag = (int) Math.Floor(Math.Floor(Math.Log10(absnum))/3);
        }
        else
        {
            mag = (int) (Math.Floor(Math.Log10(absnum))/3);
        }

        var shortNumber = number/Math.Pow(10, mag*3);

        return $"{shortNumber:0.###}{suffix[mag + 6]}";
    }
}

This should output:

3000 ==> 3k
3300 ==> 3,3k
3333 ==> 3,333k
30000 ==> 30k
300000 ==> 300k
3000000 ==> 3M
3000003 ==> 3M
0,253 ==> 253m
0,0253 ==> 25,3m
0,00253 ==> 2,53m
-0,253003 ==> -253,003m