截断号指定的小数位 [英] Truncating a number to specified decimal places

问题描述

我需要截断一个数字来2位小数，这基本上意味着
斩去额外的数字

I need to truncate a number to 2 decimal places, which basically means chopping off the extra digits.

例如：

2.919     ->      2.91

2.91111   ->     2.91

为什么呢？这就是存储数量
特定精度当SQL Server在做什么。例如，如果一个列是小数（8,2），并尝试
插入/更新多项9.1234，3和4将被砍掉。

Why? This is what SQL server is doing when storing a number of a particular precision. Eg, if a column is Decimal(8,2), and you try to insert/update a number of 9.1234, the 3 and 4 will be chopped off.

我需要做同样的事情在C＃代码

I need to do exactly the same thing in c# code.

这是我能想到这样做是不是唯一可能的方式：

The only possible ways that I can think of doing it are either:

使用stringformatter到打印出来只有
两个小数位，然后将其转换为一个小数，
如

1. Using the stringformatter to "print" it out only two decimal places, and then converting it to a decimal, eg:

  decimal tooManyDigits = 2.1345

decimal ShorterDigits = Convert.ToDecimal(tooManyDigits.ToString("0.##"));

// ShorterDigits is now 2.13

我不开心与此因为它涉及到字符串，然后
另一个字符串到十进制的转换，这似乎有点疯狂。

I'm not happy with this because it involves a to-string and then another string to decimal conversion which seems a bit mad.

使用Math.Truncate（只接受一个整数），所以我
可以用100乘以它，截断它，然后乘以100除以例如：

Using Math.Truncate (which only accepts an integer), so I can multiply it by 100, truncate it, then divide by 100. eg:

decimal tooLongDecimal = 2.1235;

tooLongDecimal = Math.Truncate(tooLongDecimal * 100) / 100;

我也不会满意这个，因为如果tooLongDecimal为0，
我会由0误差得到一个鸿沟。

I'm also not happy with this because if tooLongDecimal is 0, I'll get a divide by 0 error.

当然，有一个更好的+更简单的方法！ ？任何建议

Surely there's a better + easier way! Any suggestions?

推荐答案

您已经回答了自己的问题;看来你只是零手段误解了分裂。要做到这一点，正确的方法是倍增，截断，然后devide，像这样的：

You've answered the question yourself; it seems you just misunderstood what division by zero means. The correct way to do this is to multiply, truncate, then devide, like this:

decimal TruncateTo100ths(decimal d)
{
    return Math.Truncate(d* 100) / 100;
}

TruncateTo100ths(0m);       // 0
TruncateTo100ths(2.919m);   // 2.91
TruncateTo100ths(2.91111m); // 2.91
TruncateTo100ths(2.1345m);  // 2.13

有没有被零除这里，仅存在由100划分，这是完全安全的。

There is no division by zero here, there is only division by 100, which is perfectly safe.

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