派生小数类型 - 固定精度

发布于 2024-10-09 05:31:45 字数 586 浏览 4 评论 0原文

.NET 中是否有一种方法可以创建从十进制派生的类型，该类型将用作货币，以便将算术运算四舍五入到所需的小数位数。

如果没有，.NET 中的最佳实践是什么？

编辑（动机）：

假设我有一个价格：

125.00 Rep$

我卖了 0.25 件，相当于 31.25

现在，我有 15% 的折扣，并且计算折扣并以绝对值呈现它我将有：

31.25 * .85 = 26.5625

如果我使用其他方式：

31.25 * .15 = 4.6875

如果我让一些第三方控件截断它并显示它，例如，我可以：

26.56 +
 4.68 =
-----
31.24

如果你给每个会计师都会吃掉你的壁炉她之类的东西。

如果在这里加税，问题就会进一步加剧。

因此，不要存储尽可能多的小数并尽可能晚地四舍五入。创建一个类，使其在财务上正确并尽快将其四舍五入/截断存储。

原文

Is there a way in .NET to create a type derived from decimal that would be used as a currency, so it rounds the arithmetic operations to the desired number of decimal points.

If not, what are the best practice for it in .NET?

EDIT (motivation):

Let's say I have a price:

125.00 Rep$

and I sell 0.25 pieces of it, that amounts to 31.25

Now, I have a discount of 15%, and to calculate discount and present it in absolute value I'll have:

31.25 * .85 = 26.5625

If I use other way:

31.25 * .15 = 4.6875

If I let some 3rd party control to truncate it and display it, for example, I could have:

26.56 +
 4.68 =
-----
31.24

And every accountant will eat your hearth if you give her something like that.

Add tax here, and problem multiplies further.

So, NO storing as much decimals and rounding it as late as possible. Create a class that will do it financially correct and store it as soon as possible rounded/truncated.

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半夏半凉 2024-10-16 05:31:45

您当然不能创建从 decimal 派生的类型，因为它是一个结构体 - 并且您无法创建结构体的子类型。

不过，您可以创建自己的Currency结构，其中包含小数。您需要重载所有算术运算符，以便基本上对包含的十进制值执行算术，然后适当舍入。

例如：（

public struct Currency
{
    private readonly decimal value;

    public Currency(decimal value)
    {
        this.value = decimal.Round(value, 2);
    }

    public override string ToString()
    {
        return value.ToString();
    }

    public static Currency operator+(Currency left, Currency right)
    {
        return new Currency(left.value + right.value);
    }

    public static Currency operator-(Currency left, Currency right)
    {
        return new Currency(left.value - right.value);
    }

    public static Currency operator/(Currency left, int right)
    {
        return new Currency(left.value / right);
    }
}

class Test
{
    static void Main()
    {
        Currency currency = new Currency(15);
        Console.WriteLine(currency / 10); // Prints 1.5
        Console.WriteLine(currency / 100); // Prints 0.15
        Console.WriteLine(currency / 1000); // Prints 0.2
    }
}

显然这里还需要更多 - 特别是您需要重写 GetHashCode 和 Equals，实现 IEquatable等等）

这绝对是你想要的吗？我认为更常见的是在中间操作期间保持尽可能多的精度，并且只在最后一刻进行舍入，例如存储在数据库中或显示给用户。

You certainly can't create a type derived from decimal, as it's a struct - and you can't create subtypes of structs.

You could create your own Currency struct which contained a decimal, though. You'd want to overload all the arithmetic operators to basically perform the arithmetic on the contained decimal values and then round appropriately.

For example:

public struct Currency
{
    private readonly decimal value;

    public Currency(decimal value)
    {
        this.value = decimal.Round(value, 2);
    }

    public override string ToString()
    {
        return value.ToString();
    }

    public static Currency operator+(Currency left, Currency right)
    {
        return new Currency(left.value + right.value);
    }

    public static Currency operator-(Currency left, Currency right)
    {
        return new Currency(left.value - right.value);
    }

    public static Currency operator/(Currency left, int right)
    {
        return new Currency(left.value / right);
    }
}

class Test
{
    static void Main()
    {
        Currency currency = new Currency(15);
        Console.WriteLine(currency / 10); // Prints 1.5
        Console.WriteLine(currency / 100); // Prints 0.15
        Console.WriteLine(currency / 1000); // Prints 0.2
    }
}

(Obviously there's a lot more needed here - in particular you'll want to override GetHashCode and Equals, implement IEquatable<T> etc.)

Is this definitely what you want though? I thought it was more common to keep as much precision as you could during intermediate operations, and only round at the last moment, e.g. for storage in a database or display to a user.

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