Regular Expression: Find a specific group within other groups in VB.Net

Question

I need to write a regular expression that has to replace everything except for a single group.

E.g

IN	OUT
OK THT PHP This is it 06222021	This is it
NO MTM PYT Get this content 111111	Get this content

I wrote the following Regular Expression: (\w{0,2}\s\w{0,3}\s\w{0,3}\s)(.*?)(\s\d{6}(\s|))

This RegEx creates 4 groups, using the first entry as an example the groups are:

1. OK THT PHP
2. This is it
3. 06222021
4. Space Charachter

I need a way to:

• Replace Group 1,2,4 with String.Empty

OR

• Get Group 3, ONLY

Answer 1

You don't need 4 groups, you can use a single group 1 to be in the replacement and match 6-8 digits for the last part instead of only 6.

Note that this \w{0,2} will also match an empty string, you can use \w{1,2} if there has to be at least a single word char.

^\w{0,2}\s\w{0,3}\s\w{0,3}\s(.*?)\s\d{6,8}\s?$

• ^ Start of string
• \w{0,2}\s\w{0,3}\s\w{0,3}\s Match 3 times word characters with a quantifier and a whitespace in between
• (.*?) Capture group 1 match any char as least as possible
• \s\d{6,8} Match a whitespace char and 6-8 digits
• \s? Match an optional whitespace char
• $ End of string

Regex demo

Example code

Dim s As String = "OK THT PHP This is it 06222021"
Dim result As String = Regex.Replace(s, "^\w{0,2}\s\w{0,3}\s\w{0,3}\s(.*?)\s\d{6,8}\s?$", "$1")
Console.WriteLine(result)

Output

This is it