被除法四舍五入咬了? [英] Bitten by division rounding?

问题描述

为什么会出现以下代码:

Why does the following code:

Console.WriteLine(String.Format("{0:C0}", 2170/ 20));

收益$109"，同时做

yield "$109", while doing

Console.WriteLine(Math.Round(2170 / 20));

给我 108?

我怎样才能得到 2170/20 给我 109?

How can I get 2170 / 20 give me 109?

推荐答案

当您划分为整数类型的值时，例如 2170 和 20，运行时执行整数除法并丢弃(截断)小数.

When you divide to values of integral type, such as 2170 and 20, the runtime performs an integer division and discards (truncates) the decimal.

如果您将操作数之一更改为 float、double 或 decimal(例如，2170.0/20code> 或 2170/20m)，它将执行浮点除法，如您所料.

If you change one of the operands to a float, double, or decimal (eg, 2170.0 / 20, or 2170 / 20m), it will perform a floating-point division, as you would expect.

因此，您需要将其更改为

Therefore, you need to change it to

Console.WriteLine(Math.Round(2170.0 / 20));

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编辑

像这样:

Math.Round(2170m / 20, MidpointRounding.AwayFromZero)

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