Regex C# – optional group in the middle

Solution for Regex C# – optional group in the middle
is Given Below:

I have such source text with an optional group in the middle:

GH22-O0-TFS-SFSD 00-1-006.19135
GH22-O0-TFS-SFSD 00-1-006.1.19135

Desired value in the first case will be ‘19135’ and in the second ‘1.19135’.

Regex has to match the whole string and select all characters after first “.” – which is my Group 1. I tried to make subgroups and mark Group 3 as optional but it is not working.



How it should be changed to capture desired values?

This should work for you:


This will match the whole string and include everything after the first period in capture group 1 regardless of character type.

You can use


See the regex demo. Details:

  • ^ – start of string
  • (.*?) – Group 1: any zero or more chars other than an LF char as few as possoble (as *? is a lazy quantifier)
  • . – a dot
  • 0* – zero or more zeros
  • (d+) – Group 2: any one or more digits
  • (?:.0*(d+))? – an optional occurrence of ., zero or more zeros, then Group 3 capturing one or more digits
  • $ – end of string.

I hope I understand your goals and this should work:

  • .*?. – loosely capture everything leading up to the first period
  • ([d.]+) – capture the remaining digits and periods into capture group #1