像Stack Overflow这样的格式编号(带有K后缀的四舍五入到数千)

Question

如何用C#格式化SO这样的数字？

10,5k,......

Answer 1

像这样:( 编辑:经过测试)

static string FormatNumber(int num) {
    if (num >= 100000)
        return FormatNumber(num / 1000) + "K";
    if (num >= 10000) {
        return (num / 1000D).ToString("0.#") + "K";
    }
    return num.ToString("#,0");
}

例子:

• 1 => 1
• 23 => 23
• 136 => 136
• 6968 => 6,968
• 23067 => 23.1K
• 133031 => 133K

请注意,这将为数字> = 10 ⁸提供奇怪的值.
例如,12345678成为12.3KK.

Answer 2

下面的代码测试到int.MaxValue这不是最漂亮的代码,但效率最高.但你可以用它作为:

123.KiloFormat(); 4332.KiloFormat(); 2332124.KiloFormat(); int.MaxValue.KiloFormat(); (int1 - int2*int3).KiroFormat();

等等...

public static class Extensions
{
    public static string KiloFormat(this int num)
    {
        if (num >= 100000000)
            return (num / 1000000).ToString("#,0M");

        if (num >= 10000000)
            return (num / 1000000).ToString("0.#") + "M";

        if (num >= 100000)
            return (num / 1000).ToString("#,0K");

        if (num >= 10000)
            return (num / 1000).ToString("0.#") + "K";

        return num.ToString("#,0");
    } 
}

Answer 3

您可以像这样创建一个CustomFormater:

public class KiloFormatter: ICustomFormatter, IFormatProvider
{
    public object GetFormat(Type formatType)
    {
        return (formatType == typeof(ICustomFormatter)) ? this : null;
    }

    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        if (format == null || !format.Trim().StartsWith("K")) {
            if (arg is IFormattable) {
                return ((IFormattable)arg).ToString(format, formatProvider);
            }
            return arg.ToString();
        }

        decimal value = Convert.ToDecimal(arg);

        //  Here's is where you format your number

        if (value > 1000) {
            return (value / 1000).ToString() + "k";
        }

        return value.ToString();
    }
}

并像这样使用它:

String.Format(new KiloFormatter(), "{0:K}", 15600);

编辑:将CurrencyFormatter重命名为KiloFormatter

Answer 4

我刚写了一些提供完整的信息

public static class SIPrefix
{
    private static List<SIPrefixInfo> _SIPrefixInfoList = new
        List<SIPrefixInfo>();

    static SIPrefix()
    {
        _SIPrefixInfoList = new List<SIPrefixInfo>();
        LoadSIPrefix();
    }

    public static List<SIPrefixInfo> SIPrefixInfoList
    { 
        get 
        { 
            SIPrefixInfo[] siPrefixInfoList = new SIPrefixInfo[6];
            _SIPrefixInfoList.CopyTo(siPrefixInfoList);
            return siPrefixInfoList.ToList();
        }
    }

    private static void LoadSIPrefix()
    {
        _SIPrefixInfoList.AddRange(new SIPrefixInfo[]{
            new SIPrefixInfo() {Symbol = "Y", Prefix = "yotta", Example = 1000000000000000000000000.00M, ZeroLength = 24, ShortScaleName = "Septillion", LongScaleName = "Quadrillion"},
            new SIPrefixInfo() {Symbol = "Z", Prefix = "zetta", Example = 1000000000000000000000M, ZeroLength = 21, ShortScaleName = "Sextillion", LongScaleName = "Trilliard"},
            new SIPrefixInfo() {Symbol = "E", Prefix = "exa", Example = 1000000000000000000M, ZeroLength = 18, ShortScaleName = "Quintillion", LongScaleName = "Trillion"},
            new SIPrefixInfo() {Symbol = "P", Prefix = "peta", Example = 1000000000000000M, ZeroLength = 15, ShortScaleName = "Quadrillion", LongScaleName = "Billiard"},
            new SIPrefixInfo() {Symbol = "T", Prefix = "tera", Example = 1000000000000M, ZeroLength = 12, ShortScaleName = "Trillion", LongScaleName = "Billion"},
            new SIPrefixInfo() {Symbol = "G", Prefix = "giga", Example = 1000000000M, ZeroLength = 9, ShortScaleName = "Billion", LongScaleName = "Milliard"},
            new SIPrefixInfo() {Symbol = "M", Prefix = "mega", Example = 1000000M, ZeroLength = 6, ShortScaleName = "Million", LongScaleName = "Million"},
            new SIPrefixInfo() {Symbol = "K", Prefix = "kilo", Example = 1000M, ZeroLength = 3, ShortScaleName = "Thousand", LongScaleName = "Thousand"},
            new SIPrefixInfo() {Symbol = "h", Prefix = "hecto", Example = 100M, ZeroLength = 2, ShortScaleName = "Hundred", LongScaleName = "Hundred"},
            new SIPrefixInfo() {Symbol = "da", Prefix = "deca", Example = 10M, ZeroLength = 1, ShortScaleName = "Ten", LongScaleName = "Ten"},
            new SIPrefixInfo() {Symbol = "", Prefix = "", Example = 1M, ZeroLength = 0, ShortScaleName = "One", LongScaleName = "One"},
        });
    }

    public static SIPrefixInfo GetInfo(long amount, int decimals)
    {
        return GetInfo(Convert.ToDecimal(amount), decimals);
    }

    public static SIPrefixInfo GetInfo(decimal amount, int decimals)
    {
        SIPrefixInfo siPrefixInfo = null;
        decimal amountToTest = Math.Abs(amount);

        var amountLength = amountToTest.ToString("0").Length;
        if(amountLength < 3)
        {
            siPrefixInfo = _SIPrefixInfoList.Find(i => i.ZeroLength == amountLength).Clone() as SIPrefixInfo;
            siPrefixInfo.AmountWithPrefix =  Math.Round(amount, decimals).ToString();

            return siPrefixInfo;
        }

        siPrefixInfo = _SIPrefixInfoList.Find(i => amountToTest > i.Example).Clone() as SIPrefixInfo;

        siPrefixInfo.AmountWithPrefix = Math.Round(
            amountToTest / Convert.ToDecimal(siPrefixInfo.Example), decimals).ToString()
                                        + siPrefixInfo.Symbol;

        return siPrefixInfo;
    }
}

public class SIPrefixInfo : ICloneable
{
    public string Symbol { get; set; }
    public decimal Example { get; set; }
    public string Prefix { get; set; }
    public int ZeroLength { get; set; }
    public string ShortScaleName { get; set; }
    public string LongScaleName { get; set; }
    public string AmountWithPrefix { get; set; }

    public object Clone()
    {
        return new SIPrefixInfo()
                            {
                                Example = this.Example,
                                LongScaleName = this.LongScaleName,
                                ShortScaleName = this.ShortScaleName,
                                Symbol = this.Symbol,
                                Prefix = this.Prefix,
                                ZeroLength = this.ZeroLength
                            };

    }
}

使用:

var amountInfo = SIPrefix.GetInfo(10250, 2);
var amountInfo2 = SIPrefix.GetInfo(2500000, 0);

amountInfo.AmountWithPrefix // 10.25K
amountInfo2.AmountWithPrefix // 2M

Answer 5

SLaks代码的略微修改版本

static string FormatNumber(long num)
{
    if (num >= 100000000) {
        return (num / 1000000D).ToString("0.#M");
    }
    if (num >= 1000000) {
        return (num / 1000000D).ToString("0.##M");
    }
    if (num >= 100000) {
        return (num / 1000D).ToString("0.#k");
    }
    if (num >= 10000) {
        return (num / 1000D).ToString("0.##k");
    }

    return num.ToString("#,0");
}

这将返回以下值:

 123        ->  123
 1234       ->  1,234
 12345      ->  12.35k
 123456     ->  123.4k
 1234567    ->  1.23M
 12345678   ->  12.35M
 123456789  ->  123.5M