Regular Expression to replace the numbers in a file

Question

Hi all

There are a lot of numbers like 200 20.5 329.2...in a file. Now, I need replace every number A with A*0.8. Is there any simple method to replace original value with another based on original value?

Best Regards,

Answer 1

Try this one:

String s = "This is the number 2.5. And this is 7";
s = Regex.Replace(s, @"[+-]?\d+(\.\d*)?", m => {return (Double.Parse(m.ToString())*0.8).ToString();});
// s contains "This is the number 2. And this is 5.6"

Edit: Added the plus/minus sign as an optional character in front. To avoid catching the 5 in 3-5 as negative, you could use ((?<=\s)[+-])? instead of [+-]

Answer 2

Using lambda and slightly better handling of cases like The value is .5. Next sentence:

var s = "This is the number 2.5. And this is 7, .5, 5. Yes.";
var result = Regex.Replace(s, @"[+-]?(\d*\.)?\d+", m => (double.Parse(m.Value) * 0.8).ToString());