在C#中舍入到2位小数

Question

我有一个十进制数字,可以像下面这样:

189.182

我想这一轮最多到小数点后2位,所以输出将是以下几点:

189.19

Math类中是否内置了此功能,还是其他功能？我知道天花板功能存在,但这似乎没有做我想要的 - 它会绕到最近的int,所以在这种情况下只是'189'.

Answer 1

乘以100,呼叫上限,除以100,我认为你要求的

public static double RoundUp(double input, int places)
{
    double multiplier = Math.Pow(10, Convert.ToDouble(places));
    return Math.Ceiling(input * multiplier) / multiplier;
}

用法如下:

RoundUp(189.182, 2);

这通过将小数点右移2个位置(因此它位于最后8位的右侧)然后执行上限操作,然后将小数点移回其原始位置来工作.

Answer 2

您可以使用:

decimal n = 189.182M;
n = System.Math.Ceiling (n * 100) / 100;

可以在此处找到各种舍入函数的说明.

Answer 3

在 .NET Core 3.0 及更高版本中，可以通过 MidpointRounding 枚举使用三种附加舍入策略。此外MidpointRounding.AwayFromZero，MidpointRounding.ToEven它现在还包括：

 1. MidpointRounding.ToNegativeInfinity
 2. MidpointRounding.ToPositiveInfinity
 3. MidpointRounding.ToZero

对于这个特定问题，您需要使用MidpointRounding.ToPositiveInfinity，这将始终将数字向上舍入。请注意，这仅在数字非负数时才有效。有关示例，请参阅下表。

原始号码	至负无穷	至正无穷	归零
3.55	3.5	3.6	3.5
2.83	2.8	2.9	2.8
2.54	2.5	2.6	2.5
2.16	2.1	2.2	2.1
-2.16	-2.2	-2.1	-2.1
-2.54	-2.6	-2.5	-2.5
-2.83	-2.9	-2.8	-2.8
-3.55	-3.6	-3.5	-3.5

有关中点舍入的更多信息，请参阅https://learn.microsoft.com/en-us/dotnet/api/system.midpointrounding

当然还有让它工作的代码：

// function explained: Math.Round(number, amount of decimals, MidpointRounding);
decimal number = 189.182m;
number =  Math.Round(number, 2, MidpointRounding.ToPositiveInfinity);
// result: number = 189.19

Answer 4

            var numberToBeRound1 = 4.125;
            var numberToBeRound2 = 4.175;
            var numberToBeRound3 = 4.631;
            var numberToBeRound4 = 4.638;
            var numberOfDecimalPlaces = 2;
            var multiplier = Math.Pow(10, numberOfDecimalPlaces);

            //To Round Up => 4.13
            var roundedUpNumber = Math.Ceiling(numberToBeRound1 * multiplier) / multiplier;

            //To Round Down => 4.12
            var roundedDownNumber = Math.Floor(numberToBeRound1 * multiplier) / multiplier;

            //To Round To Even => 4.12
            var roundedDownToEvenNumber = Math.Round(numberToBeRound1, numberOfDecimalPlaces, MidpointRounding.ToEven);

            //To Round To Even => 4.18
            var roundedUpToEvenNumber = Math.Round(numberToBeRound2, numberOfDecimalPlaces, MidpointRounding.ToEven);

            //To Round To Away From Zero => 4.63
            var roundedDownToAwayFromZero = Math.Round(numberToBeRound3, numberOfDecimalPlaces, MidpointRounding.AwayFromZero);

            //To Round To Away From Zero => 4.64
            var roundedUpToAwayFromZero2 = Math.Round(numberToBeRound4, numberOfDecimalPlaces, MidpointRounding.AwayFromZero);