using System;

​

public static class Program

{

    public static void Main()

    {

        var temp = 4.56769983291626;

        //Console.WriteLine(ApplySignificantFigures(temp));

        Console.WriteLine(string.Format("Truncate: {0}",TruncateToSignificantDigits(temp, 3)));

        Console.WriteLine(string.Format("Round: {0}",TruncateToSignificantDigits(temp, 3)));

        //Console.WriteLine(NewRoundToSignificantDigits(temp, 3));

    }

​

    public static double ApplySignificantFigures(double value)

    { // 0.4621513686751344

        return TruncateToSignificantDigits(RoundToSignificantDigits(value, 3), 3);

    }

​

    private static double RoundToSignificantDigits(double d, int digits)

    {

        double scale = Math.Pow(10, Math.Floor(Math.Log10(Math.Abs(d))) + 1);

        return scale * Math.Round(d / scale, digits);

    }

​

    private static double TruncateToSignificantDigits(double d, int digits)

    {

        double scale = Math.Pow(10, Math.Floor(Math.Log10(Math.Abs(d))) + 1 - digits);

        return scale * Math.Truncate(d / scale);

    }

​

    private static double NewRoundToSignificantDigits(double d, int digits)

    {

        if (d == 0.0)

        {

            return 0.0;

        }

        else

        {

            double leftSideNumbers = Math.Floor(Math.Log10(Math.Abs(d))) + 1;

            double scale = Math.Pow(10, leftSideNumbers);

            double result = scale * Math.Round(d / scale, digits, MidpointRounding.AwayFromZero);

            // Clean possible precision error.

            if ((int)leftSideNumbers >= digits)

            {

                return Math.Round(result, 0, MidpointRounding.AwayFromZero);

            }

            else

            {

                return Math.Round(result, digits - (int)leftSideNumbers, MidpointRounding.AwayFromZero);

            }

        }

    }

}