Regex Substring or Left Equivalent

Question

Greetings beloved comrades.

I cannot figure out how to accomplish the following via a regex.

I need to take this format number 201101234 and transform it to 11-0123401, where digits 3 and 4 become the digits to the left of the dash, and the remaining five digits are inserted to the right of the dash, followed by a hardcoded 01.

I've tried http://gskinner.com/RegExr, but the syntax just defeats me.

This answer, Equivalent of Substring as a RegularExpression, sounds promising, but I can't get it to parse correctly.

I can create a SQL function to accomplish this, but I'd rather not hammer my server in order to reformat some strings.

Thanks in advance.

Answer 1

You can try this:

var input = "201101234";
var output = Regex.Replace(input, @"^\d{2}(\d{2})(\d{5})$", "${1}-${2}01");

Console.WriteLine(output); // 11-0123401

This will match:

• two digits, followed by
• two digits captured as group 1, followed by
• five digits captured as group 2

And return a string which replaces that matched text with

• group 1, followed by
• a literal hyphen, followed by
• group 2, followed by
• a literal 01.

The start and end anchors ( ^ / $ ) ensure that if the input string does not exactly match this pattern, it will simply return the original string.