Question

The string can contains ints, floats and hexadecimal numbers for example.

“This a string than can have -345 and 57 and could also have 35.4656 or a subtle 0xF46434 and more”

What could I use to find these numbers in C#?

Answer 1

Use something along these lines: (I wrote it myself, so I’m not going to say it’s all-inclusive for whatever sort of numbers you’re looking to find, but it works for your example)

var str = "123 This a string than can have -345 and 57 and could also have 35.4656 or a subtle 0XF46434 and more like -0xf46434";
var a = Regex.Matches(str, @"(?<=(^|[^a-zA-Z0-9_^]))(-?\d+(\.\d+)?|-?0[xX][0-9A-Fa-f]+)(?=([^a-zA-Z0-9_]|$))");
foreach (Match match in a)
{
    //do something
}

Regex seems to be a write-only language, (i.e. incredibly hard to read) so I’ll break it down so you can understand: (?<=(^|[^a-zA-Z0-9_^])) is a lookbehind to break it by a word boundary. I can’t use \b because it considers - a boundary character, so it would only match 345 instead of -345. -?\d+(\.\d+)? matches decimal numbers, optionally negative, optionally with fractional digits. -?0[xX][0-9A-Fa-f]+ matches hexadecimal numbers, case insensitive, optionally negative. Finally, (?=([^a-zA-Z0-9_]|$)) is a lookahead, again as a word boundary. Note that in the first boundary, I allowed for the start of the string, and here I allow for the end of the string.