字符串格式数字为数百万,数字为四舍五入

Question

我正在尝试格式化显示的价格,我想显示一个带有百万(M)或数千(K)后缀的数字,但只能显示最多3个值,向下舍入.

我发现这个问题与我想要的非常接近,但是没有处理舍入(特别是,总是向下舍入)

同样,对于这个问题,你无法控制舍入.

样本输入/预期输出:

1 = 1
10 = 10
100 = 100
1000 = 1K
100000 = 100K
125000 = 125K
125900 = 125K
1000000 = 1M
1250000 = 1.25M
1258000 = 1.25M
10000000 = 10M
10500000 = 10.5M
100000000 = 100M
100100000 = 100M

我基本上只想显示3个值.

我看不出我如何使用","自定义说明符并指定舍入.

我最初的想法表明我需要使用上面的Math.Floor和一些.ToString()格式化魔法的组合,但我不确定从哪里开始.

有人可以帮我吗？

提前致谢.

Answer 1

这应该有所帮助,并结合您链接到的其他问题中的一种格式化技巧.

  internal long MaxThreeSignificantDigits(long x)
  {
     int i = (int)Math.Log10(x);
     i = Math.Max(0, i - 2);
     i = (int)Math.Pow(10, i);
     return x / i * i;
  }

编辑:

好的,这个怎么样？

 Console.WriteLine(SO30180672.FormatNumber(1));
 Console.WriteLine(SO30180672.FormatNumber(12));
 Console.WriteLine(SO30180672.FormatNumber(123));
 Console.WriteLine(SO30180672.FormatNumber(1234));
 Console.WriteLine(SO30180672.FormatNumber(12345));
 Console.WriteLine(SO30180672.FormatNumber(123456));
 Console.WriteLine(SO30180672.FormatNumber(1234567));
 Console.WriteLine(SO30180672.FormatNumber(12345678));
 Console.WriteLine(SO30180672.FormatNumber(123456789));

以下是部分复制:https://stackoverflow.com/a/23384710/253938

   internal class SO30180672
   {
      internal static string FormatNumber(long num)
      {
         num = MaxThreeSignificantDigits(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("0k");
         if (num >= 100000)
            return (num / 1000D).ToString("0.#k");
         if (num >= 1000)
            return (num / 1000D).ToString("0.##k");
         return num.ToString("#,0");
      }


      internal static long MaxThreeSignificantDigits(long x)
      {
         int i = (int)Math.Log10(x);
         i = Math.Max(0, i - 2);
         i = (int)Math.Pow(10, i);
         return x / i * i;
      }
   }

编辑2 - 非常感谢@Rhexis

   internal class SO30180672
   {
      internal static void RunTest()
      {
         Console.WriteLine(FormatNumber(1));
         Console.WriteLine(FormatNumber(10));
         Console.WriteLine(FormatNumber(100));
         Console.WriteLine(FormatNumber(1000));
         Console.WriteLine(FormatNumber(10000));
         Console.WriteLine(FormatNumber(100000));
         Console.WriteLine(FormatNumber(125000));
         Console.WriteLine(FormatNumber(125900));
         Console.WriteLine(FormatNumber(1000000));
         Console.WriteLine(FormatNumber(1250000));
         Console.WriteLine(FormatNumber(1258000));
         Console.WriteLine(FormatNumber(10000000));
         Console.WriteLine(FormatNumber(10500000));
         Console.WriteLine(FormatNumber(100000000));
         Console.WriteLine(FormatNumber(100100000));
      }

      private static string FormatNumber(long num)
      {
         // Ensure number has max 3 significant digits (no rounding up can happen)
         long i = (long)Math.Pow(10, (int)Math.Max(0, Math.Log10(num) - 2));
         num = num / i * i;

         if (num >= 1000000000)
            return (num / 1000000000D).ToString("0.##") + "B";
         if (num >= 1000000)
            return (num / 1000000D).ToString("0.##") + "M";
         if (num >= 1000)
            return (num / 1000D).ToString("0.##") + "K";

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

Answer 2

这是我的测试输出代码

1249            1.24K
12499           12.4K
124999          124K
1249999         1.24M
12499999        12.4M
124999999       124M
1249999999      1.24B

代码最多输出三位数.

    static string FormatNumber(uint n)
    {
        if (n < 1000)
            return n.ToString();

        if (n < 10000)
            return String.Format("{0:#,.##}K", n - 5);

        if (n < 100000)
            return String.Format("{0:#,.#}K", n - 50);

        if (n < 1000000)
            return String.Format("{0:#,.}K", n - 500);

        if (n < 10000000)
            return String.Format("{0:#,,.##}M", n - 5000);

        if (n < 100000000)
            return String.Format("{0:#,,.#}M", n - 50000);

        if (n < 1000000000)
            return String.Format("{0:#,,.}M", n - 500000);

        return String.Format("{0:#,,,.##}B", n - 5000000);
    }

Answer 3

由于格式本质上会根据范围而变化，因此您很可能需要一些类似于下面的条件格式。我只测试了提供的示例集，因此请确保这适用于整个预期值范围。

class Program
{
    static void Main(String[] args)
    {
        Console.WriteLine(RoundAndFormat(1));
        Console.WriteLine(RoundAndFormat(10));
        Console.WriteLine(RoundAndFormat(100));
        Console.WriteLine(RoundAndFormat(1000));
        Console.WriteLine(RoundAndFormat(100000));
        Console.WriteLine(RoundAndFormat(125000));
        Console.WriteLine(RoundAndFormat(125900));
        Console.WriteLine(RoundAndFormat(1000000));
        Console.WriteLine(RoundAndFormat(1250000));
        Console.WriteLine(RoundAndFormat(1258000));
        Console.WriteLine(RoundAndFormat(10000000));
        Console.WriteLine(RoundAndFormat(10500000));
        Console.WriteLine(RoundAndFormat(100000000));
        Console.WriteLine(RoundAndFormat(100100000));

        Console.ReadLine();
    }

    public static String RoundAndFormat(Int32 value)
    {
        var result = String.Empty;
        var negative = value < 0;
        if (negative) value = value * -1;

        if (value < 1000)
        {
            result = value.ToString();
        }
        else if (value < 1000000)
        {
            result = RoundDown(value / 1000.0, 0) + "K";
        }
        else if (value < 100000000)
        {
            result = RoundDown(value / 1000000.0, 2) + "M";
        }
        else if (value < 10000000000)
        {
            result = RoundDown(value / 1000000.0, 0) + "M";
        }

        if (negative) return "-" + result;
        return result;
    }

    public static Double RoundDown(Double value, Int32 digits)
    {
        var pow = Math.Pow(10, digits);
        return Math.Truncate(value * pow) / pow;
    }