string replace with regex while ignoring a pattern

Question

2.00/5 (1 vote)

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.NET3.5

VS2008

, +

Hello, i want to create a regex to be able to replace a string with another string while also making sure that a particular pattern is avoided from being replaced.

Eg : string is - I wanted to buy a house and this house is so good that i will {buy|purchase|rent|acquire} this place

The application should replace buy with purchase but not in the brackets. I mean all the occurences of buy should be replaced with purchase but ignore the ones that fall under {}.

The regex that i build for the brackets is this :

Dim regex As New Regex("{([^{}]+)}")

but please help me to create a regex where i can replace string and also exclude the above pattern.

the two individual expression would be like :

rgx = New Regex("buy", RegexOptions.IgnoreCase)

Dim regex As New Regex("{([^{}]+)}")

how do i merge the two to include first and exclude second one?

Posted 13-Nov-11 16:27pm

amit_upadhyay

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Comments

Prerak Patel 13-Nov-11 22:44pm

You mean, the output should be - I wanted to purchase a house and this house is so good that i will {buy|purchase|rent|acquire} this place?

amit_upadhyay 13-Nov-11 22:47pm

yup exactly.

2 solutions

Solution 2

Solution for your problem is the below method System.Text.RegularExpression namespace,

C#

Regex.Replace

More details at: http://msdn.microsoft.com/en-us/library/h0y2x3xs.aspx[^]

Posted 13-Nov-11 16:58pm

Ganesan Senthilvel

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Prerak Patel · Accepted Answer · 2011-11-13T16:54:00

Solution 1

(?!{[^{]*)buy(?![^{}]*})
This is what you want. This regex will get you the buy word not enclosed in {}.

You can match multiple words like (?!{[^{]*)buy|purchase(?![^{}]*})
You can do it like

VB

Dim rgx As New Regex("(?!{[^{]*)buy|purchase(?![^{}]*})")
Dim result As String = rgx.Replace(input, replacement) 'where input will be your content and replacement will be the word to be placed

Posted 13-Nov-11 16:54pm

Prerak Patel

Updated 13-Nov-11 17:44pm

v2

Comments

amit_upadhyay 13-Nov-11 23:33pm

hey thanks. it works great. But iam stuck with implementing this into my main program which is a slightly modified :

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 & "(?![^{}]*})", RegexOptions.IgnoreCase)
Dim z As Integer = 0

rpl = rgx.Replace(rpl, "zzzzxxxxzzzz")

Catch ex As Exception

End Try
End If

Loop

fil2.Close()

RichTextBox1.Text = rpl

currently do you see anything which can be wrong with this code? What it is doing is reading a text file, splitting the line at "|" and then count the number of words in first segment. Then it will create a pattern dynamically including the split word instead of "buy". The output is not what i want.

with the above string i get :

zxzxzxzxzxzxzxzxzx zxzxzxzxzxzxzxzxzx zxzxzxzxzxzxzxzxzx to zxzxzxzxzxzxzxzxzx buy zxzxzxzxzxzxzxzxz zxzxzxzxzxzxzxzxzx xzxzxzxzxzxzxzxzx xzxzxzxzxzxzxzxzx ho zxzxzxzxzxzxzxzxzx zxzxzxzxzxzxzxzxzx zxzxzxzxzxzxzxzxzx d zxzxzxzxzxzxzxzxzx this zxzxzxzxzxzxzxzxzx house zxzxzxzxzxzxzxzxzx is zxzxzxzxzxzxzxzxz zxzxzxzxzxzxzxzxzx xzxzxzxzxzxzxzxz zxzxzxzxzxzxzxzxzx xzxzxzxzxzxzxzxzx good zxzxzxzxzxzxzxzxzx that zxzxzxzxzxzxzxzxzx i zxzxzxzxzxzxzxzxzx will zxzxzxzxzxzxzxzxzx {buy|purchase|rent|acquire} zxzxzxzxzxzxzxzxzx this zxzxzxzxzxzxzxzxzx place

Prerak Patel 13-Nov-11 23:45pm

Updated the answer. You can match multiple words with regex. If this helped, mark as answer.

Wayne Gaylard 14-Nov-11 0:58am

Nice tutoring +5!