如何转换比例串翻番？ [英] How to convert percentage string to double?

问题描述

我有像1.5％的字符串，并希望将其转换为double值。

I have a string like "1.5%" and want to convert it to double value.

这是可以做到用下面简单的：

It can be done simple with following:

public static double FromPercentageString(this string value)
{
    return double.Parse(value.SubString(0, value.Length - 1)) / 100;
}

但我并不想用这个方法解析

but I don't want to use this parsing approach.

时使用的IFormatProvider或任何其他方式这样呢？

Is any other approach with IFormatProvider or something like this?

推荐答案

如果你在乎捕获格式错误，我会用TrimEnd而不是取代。更换将使格式错误漏过。

If you care about catching formatting errors, I would use TrimEnd rather than Replace. Replace would allow formatting errors to pass undetected.

var num = decimal.Parse( value.TrimEnd( new char[] { '%', ' ' } ) ) / 100M;

这将确保该值必须是一些十进制数后跟任意数量的空格和百分号，即，它至少必须在正确的格式值开始。为了你可能想拆就'％'，不删除空条目，然后确保只有两个结果，第二个是空的更precise。首先应该是要转换的值。

This will ensure that the value must be some decimal number followed by any number of spaces and percent signs, i.e, it must at least start with a value in the proper format. To be more precise you might want to split on '%', not removing empty entries, then make sure that there are only two results and the second is empty. The first should be the value to convert.

var pieces = value.Split( '%' );
if (pieces.Length > 2  || !string.IsNullOrEmpty(pieces[1]))
{ 
    ... some error handling ... 
}
var num = decimal.Parse( pieces[0] ) / 100M;

使用更换可以让你成功，并错误地IMO，解析之类的东西：

Using Replace will allow you to successfully, and wrongfully IMO, parse things like:

• 1.5％


• 1％。5


• 1％，5

在addtion到 1.5％

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