Format string with regex in c#

Question

I would like to format a string that looks like this

BPT4SH9R0XJ6

Into something that looks like this

BPT4-SH9R-0XJ6

The string will always be a mix of 12 letters and numbers

Any advice will be highly appreciated, thanks

Answer 1

Try Regex.Replace(input, @"(\w{4})(\w{4})(\w{4})", @"$1-$2-$3");

Regex is often derided, but is a pretty neat way of doing what you need. Can be extended to more complex requirements that are difficult to meet using string methods.

Answer 2

You can use "(.{4})(.{4})(.{4})" as your expression and "$1-$2-$3" as your replacement. This is, however, hardly a good use for regexp: you can do it much easier with Substring.

var res = s.Substring(0,4)+"-"+s.Substring(4,4)+"-"+s.Substring(8);