Question

I am trying to build an application which does the following :

1) write some text in a richtextbox

---

2) when user clicks a button, the app will replace the text with another text in {} braces.

what I want is that the next time, the regex searches for any text it should exclude those which are present in {}.

for eg :

my world is good world and a happy world and will be a better world for everyone.

first pass – change word “world”

my {world|happy place|home} is good {world|happy place|home} and a happy {world|happy place|home} and will be a better {world|happy place|home} for everyone.

second pass – change word “happy”

in this pass I want the regex to ignore all instances which are surrounded by {}. notice word happy comes in {world|happy place|home}, but it should not be touched.

now could anyone please help me with building this regex?

In simple terms I want to include the word and exclude everything that falls between {}. Also please note that word can be a string.

for eg : sometimes I might want to replace the string “happy place”.

any other logic other than regex can also help.

my code is :

Dim fil2 As New StreamReader("new2.txt")

    Dim i As Integer = 0
    Dim start2 As Integer = 0
    Dim rgx As Regex

    Dim rpl As String = RichTextBox1.Text

    Do While fil2.Peek > -1
        Dim StringToCheck As String = fil2.ReadLine()
        Dim prev As String = StringToCheck.Split("|")(0).Trim()

        If (StringToCheck.Split("|")(0).Split(" ").Count >= 2) Then
            Try
                rgx = New Regex("(?<=(^|})[^{]*)" & prev & "(?=[^}]*($|{))")
                Dim z As Integer = 0

                rpl = rgx.Replace(rpl, "{" & StringToCheck & "}")


            Catch ex As Exception

            End Try
        End If


    Loop

    fil2.Close()

    rpl = rpl.Replace("{?  ?|?  ?|? ! ?}", " ")
    RichTextBox1.Text = rpl
    MsgBox("done")

Answer 1

You can use lookaheads and lookbehinds:

"(?<=(^|})[^{]*)happy(?=[^}]*($|{))"