使用正则表达式将字符串的一部分转换为double

Question

My application seem crash on "wrong format", I have this:

Match m = Regex.Match(value, "[0-9]+[.[0-9]+]?");
double number = Convert.ToDouble(m.Value);
return number;

Point is to make string values like this: 114.6W, 120.6W. into values I can sort. My function that I wrote is suppose to turn any string into a 9999.9999 double value, but it crash on Convert.ToDouble() . Saying wrong input format?

Answer 1

The problem is with your regex: it should read

[0-9]+(\.[0-9]+)?

[.[0.9]+] (which I am surprised parses at all) is a character class looking for any character in the following set: a dot, an opening and closing bracket, 0 to 9, or a plus sign.

Answer 2

Maybe the . is not the decimal separator for the culture you are using. Try specifying InvariantCulture when parsing:

double number = Convert.ToDouble(m.Value, CultureInfo.InvariantCulture);

Answer 3

您必须用括号替换方括号

Match m = Regex.Match(value, @"[0-9]+(?:\.[0-9]+)?");

Answer 4

If it is guaranteed to always be a decimal number followed by a single letter, then:

var word = "120.6W";
var d = Decimal.Parse(word.Substring(0,word.Length-1));

Answer 5

Try these two regexes, you may need to test and adjust to your needs

this one will grab all numbers including the . , but only if followed by a W (won't grab the w)

(?i)\d+\.\d+(?=w)

this one will grab all the digits regardless what's after it

\d+\.\d+

or if your data sets consists of only the numbers plus one letter and nothing in front or after it, do as @paul suggests, just strip the last char