Engineering notation in C#?

Question

Is there any code out there (or a built-in function) which allows outputting a floating point number in engineering notation?

For example, 1.5e-4 would

Answer 1

ICustomFormmatter using a private dictionary for the symbols.

class EngNotationFormatter : IFormatProvider, ICustomFormatter
{
    private readonly Dictionary notationSymbols = new Dictionary
    {
        {double.NegativeInfinity, ""}, //Handles when value is 0
        {-24, "y"},
        {-21, "z"},
        {-18, "a"},
        {-15, "f"},
        {-12, "p"},
        {-9, "n"},
        {-6, "μ"},
        {-3, "m"},
        {0, ""},
        {3, "k"},
        {6, "M"},
        {9, "G"},
        {12, "T"},
        {15, "P"},
        {18, "E"},
        {21, "Z"},
        {24, "Y"},
    };

    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        double value = Convert.ToDouble(arg);
        double engExponent = Math.Floor(Math.Log10(value) / 3) * 3;

        return (value * Math.Pow(10, (int)-engExponent)) + notationSymbols[engExponent];
    }

    public object GetFormat(Type formatType)
    {
        if (formatType == typeof(ICustomFormatter))
            return this;
        else
            return null;
    }
}

Example use

(0.00005678).ToString(new EngNotationFormatter()); //56.78μ
(0.1234).ToString(new EngNotationFormatter());     //123.4m
(0).ToString(new EngNotationFormatter());          //0
(1300).ToString(new EngNotationFormatter());       //1.3k
(19000).ToString(new EngNotationFormatter());      //19k