VB.NET Regex Replacement

Question

I have a list of fields named flav x (other text) that go 1 through 10. For example, I might have:

flav2PGPct

I need to turn it to

flav12PGPct

I need to replaced 1 through 10 with 11 through 20 using VB.NET's Replace function with Regex, but I can't get it working right.

Can anyone help?

Here's what I've tried:

(\.)flav*[1-9]

I have no idea what to place in the replacement box...

Answer 1

使用此正则表达式进行搜索： (flav)(\\d\\w*)并使用该正则表达式进行替换： ${1}1$2 。

Answer 2

I'd use 2 regex runs to obtain the desired result because it is not possible to use a replacement literal with alternatives.

The first regex would replace 10 to 20 and the second will handle 1 to 9 digits:

Dim rx1to9 As Regex = New Regex("(?<=\D|^)[1-9](?=\D|$)") '1 - 9
Dim rx10 As Regex = New Regex("(?<=\D|^)10(?=\D|$)") '10
Dim str As String = "flav2PG10Pct101"
Dim result = rx10.Replace(str, "20")
result = rx1to9.Replace(result, "1$&")
Console.WriteLine(result)

See IDEONE demo (output is flav12PG20Pct101 )

Regex explanation :

• (?<=\\D|^) - A positive look-behind that makes sure there is no digit ( \\D ) or start of string ( ^ ) before...
• [1-9] - a single digit from 1 to 9 (or, in the second regex, 10 matching literal 10 )
• (?=\\D|$) - A positive look-ahead that makes sure there is no digit ( \\D ) or the end of string ( $ ) after the digit.

If you must check if flav is present in the string, you may use a bit different look-behind: (?<=flav\\D*|^) , or - if spaces should not occur between flav and the digit: (?<=flav[^\\d\\s]*|^) .

Answer 3

Regexes work best with strings rather than numbers, so an easy way is to use a regex to get the parts of the string you want to adjust and then concatenate the calculated part in a string:

Option Strict On
Option Infer On

Imports System.Text.RegularExpressions

Module Module1

    Sub Main()
        Dim re As New Regex("^flav([0-9]+)(.*)$")
        Dim s = "flav1PGPct"
        Dim t = ""
        Dim m = re.Match(s)
        If m.Success Then
            t = CStr(Integer.Parse(m.Groups(1).Value) + 10)
            t = "flav" & t & m.Groups(2).Value
        End If
        Console.WriteLine(t)

        Console.ReadLine()

    End Sub

End Module