从字符串开头提取小数 [英] Extract decimal from start of string

问题描述

我有一个字符串，例如 5.5kg 或 7.90gram ，我想获取 5.5 或 7.90 作为十进制值。我如何在C＃中得到这样的结果以及我的字符串始终以十进制开头的另一件事。

I have a string like 5.5kg or 7.90gram and I want to get 5.5 or 7.90 as a decimal value. How can I get such result in C# and one more thing that my string will always starts with decimal.

这是我的代码，只要遇到除小数点以外的其他内容，都会抛出错误。

Here is my code that throws an error whenever it will encounter anything except a decimal.

string weight = attributeValue;
if (!string.IsNullOrEmpty(weight))
{
    product.Weight = Convert.ToDecimal(attributeValue);
}
else
{
    product.Weight = 0.00m;
}

推荐答案

我将创建一个正则表达式匹配前导号码部分。这部分取决于您是否总是有小数点，是否要为数千个分隔符使用逗号，是否始终使用。例如小数点等等。

I would create a regular expression matching the leading number part. This will partly depend on whether you will always have a decimal point, whether you want to allow commas for thousands separators, whether it will always use . as the decimal point, etc. It might look something like this though:

^-?\d+(?:\.\d+)?

然后将正则表达式与您的文本进行匹配，取匹配的值（如果成功）并在该值上使用 decimal.Parse 或 double.Parse ：

Then match that regular expression against your text, take the value of the match (if it's successful) and use decimal.Parse or double.Parse on that value:

Regex regex = new Regex(@"^-?\d+(?:\.\d+)?");
Match match = regex.Match(text);
if (match.Success)
{
    weight = decimal.Parse(match.Value, CultureInfo.InvariantCulture);
}

请注意，对于自然值，例如质量，您可能会与十进制相比，使用 double 更好。后者更适用于人工值，例如货币，自然最好用十进制表示并具有精确值。这取决于您在做什么。

Note that for "natural" values such as mass, you may be better off with double than decimal. The latter is more appropriate for "artificial" values such as currency, which are naturally best expressed in decimal and have exact values. It depends on what you're doing though.

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