CODEWITHSUNDEEP
regexvb.net
samgi
samgi

Reputation: 225

Replace the second char of a string

I have a string variable. 

Dim str As String = "ABBCD"

I want to replace only the second 'B' character of str (I mean the second occurrence)

my code

Dim regex As New Regex("B")
Dim result As String = regex.Replace(str, "x", 2)

'result: AxxCD
'but I want: ABxCD

What's the easiest way to do this with Regular Expressions.

thanks

Upvotes: 2

Views: 331

Answers (6)

Aly Elhaddad
Aly Elhaddad

Reputation: 1943

    Dim str As String = "ABBCD"
    Dim matches As MatchCollection = Regex.Matches(str, "B")
    If matches.Count >= 2 Then
        str = str.Remove(matches(1).Index, matches(1).Length)
        str = str.Insert(matches(1).Index, "x")
    End If

First we declare the string 'str', then find the matches of "B". If we found two results or more, replace the second result with "x".

Upvotes: 1

justaguest
justaguest

Reputation: 1

'Alternative way to replace the second occurrence
    'only of B in the string with X
    Dim str As String = "ABBCD"
    Dim pattern As String = "B"
    Dim reg As Regex = New Regex(pattern)
    Dim replacement As String = "X"
    'find position of second B
    Dim secondBpos As Integer = Regex.Matches(str, pattern)(1).Index
    'replace that B with X
    Dim result As String = reg.Replace(str, replacement, 1, secondBpos)
    MessageBox.Show(result)

Upvotes: 0

Pedro Lobito
Pedro Lobito

Reputation: 98901

I assume BB was just an example, it can be CC, DD, EE, etc..
Based on that, the regex below will replace any repeated character in the string.

resultString = Regex.Replace(subjectString, @"(\w)\1", "$1x");

Upvotes: 1

Ulugbek Umirov
Ulugbek Umirov

Reputation: 12797

If ABCABCABC should produce ABCAxCABC, then the following regex will work:

(?<=^[^B]*B[^B]*)B

Regular expression visualization

Usage:

Dim result As String = Regex.Replace(str, "(?<=^[^B]*B[^B]*)B", "x")

Upvotes: 1

revo
revo

Reputation: 48711

Use a positive lookbehind:

Dim regex As New Regex("(?<=B)B")

Live demo

Upvotes: 1

Ron Rosenfeld
Ron Rosenfeld

Reputation: 60174

How about:

resultString = Regex.Replace(subjectString, @"(B)\1", "$+x");

Upvotes: 1

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