C# 格式化货币

发布于 2024-08-28 02:14:49 字数 1619 浏览 6 评论 0原文

我看到 C# 中的货币四舍五入的有趣情况（VS 2008 SP1）。下面是测试用例的图片：

alt text http://img697.imageshack.us /img697/8500/testcases.png

我预计案例五、六和七（我的错误是没有在输出中对它们进行编号）将数字四舍五入到一便士。

这是我的测试代码：

static void Main(string[] args)
{
    decimal one = 10.994m;
    decimal two = 10.995m;
    decimal three = 1.009m;
    decimal four = 0.0044m;
    decimal five = 0.0045m;
    decimal six = 0.0046m;
    decimal seven = 0.0049m;
    decimal eight = 0.0050m;

    Console.WriteLine(one + ": " + one.ToString("C"));
    Console.WriteLine(two + ": " + two.ToString("C"));
    Console.WriteLine(three + ": " + three.ToString("C"));
    Console.WriteLine(four + ": " + four.ToString("C"));
    Console.WriteLine(five + ": " + five.ToString("C"));
    Console.WriteLine(six + ": " + six.ToString("C"));
    Console.WriteLine(seven + ": " + seven.ToString("C"));
    Console.WriteLine(eight + ": " + eight.ToString("C"));

    Console.ReadLine();
}

当我反映到 .ToString(string format) 以查看发生了什么时，我发现

public string ToString(string format)
{
    return Number.FormatDecimal(this, format, NumberFormatInfo.CurrentInfo);
}

其中调用了

[MethodImpl(MethodImplOptions.InternalCall)]
public static extern string FormatDecimal(
    decimal value, 
    string format, 
    NumberFormatInfo info);

Is There somelogic in that call 表明我当前的 NumberFormatInfo 区域性设置的粒度是两位小数货币的位数，所以不要让千分之十位将数字累加起来，因为它微不足道？

这个方法是如何实现的呢？我们是进入了位移领域，还是发生了其他事情？

感谢您的任何见解。

原文

I am seeing an intriguing situation rounding Currency in C# (VS 2008 SP1). Below is an image of the test cases:

alt text http://img697.imageshack.us/img697/8500/testcases.png

I was expecting cases five, six, and seven (my bad on not numbering them in the output) to round the number up to a penny.

Here is my test code:

static void Main(string[] args)
{
    decimal one = 10.994m;
    decimal two = 10.995m;
    decimal three = 1.009m;
    decimal four = 0.0044m;
    decimal five = 0.0045m;
    decimal six = 0.0046m;
    decimal seven = 0.0049m;
    decimal eight = 0.0050m;

    Console.WriteLine(one + ": " + one.ToString("C"));
    Console.WriteLine(two + ": " + two.ToString("C"));
    Console.WriteLine(three + ": " + three.ToString("C"));
    Console.WriteLine(four + ": " + four.ToString("C"));
    Console.WriteLine(five + ": " + five.ToString("C"));
    Console.WriteLine(six + ": " + six.ToString("C"));
    Console.WriteLine(seven + ": " + seven.ToString("C"));
    Console.WriteLine(eight + ": " + eight.ToString("C"));

    Console.ReadLine();
}

When I reflected into .ToString(string format) to see what was going on I found

public string ToString(string format)
{
    return Number.FormatDecimal(this, format, NumberFormatInfo.CurrentInfo);
}

which has the call to

[MethodImpl(MethodImplOptions.InternalCall)]
public static extern string FormatDecimal(
    decimal value, 
    string format, 
    NumberFormatInfo info);

Is there some logic in that call that says the granularity for my current culture settings for NumberFormatInfo is two decimal places for currencty so don't let the ten thousandths place roll the number up because it is insignificant?

How is this method implemented? Are we into bit shift land, or is something else going on?

Thanks for any insights.

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