How to replace words in a text file using C#

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4.67/5 (3 votes)

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Hello All,

Kindly help me out with this.

I have a text file and this has many lines,(some line have incorrect words), and I need to replace the incorrect words by correct words.

If I follow this

String strFile = File.ReadAllText("c:\\File1.txt");

strFile = strFile.Replace("oldvalue", "newvalue");

File.WriteAllText("c:\\File1.txt", strFile);

(Which I actually dont want to follow) I have other problems line some correct words getting changed.
Is there any other way to do this.

Posted 20-Jul-10 4:35am

asjadazeez

Updated 15-Dec-22 22:20pm

Dalek Dave

v2

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Dalek Dave 21-Jul-10 19:02pm

Edited for Grammar, Syntax and Capitalisation.

3 solutions

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#realJSOP · Answer 1 · 2010-07-21T12:22:00

Solution 2

A variation of Toli's code:

string text = File.ReadAllText(@"c:\File1.txt");
text = text.Replace("old value","new stuff");
File.WriteAllText(@"c:\File1.txt", text);

Look! No Regex!

Posted 21-Jul-10 12:22pm

#realJSOP

Comments

Toli Cuturicu 26-Jul-10 13:51pm

Reason for my vote of 1
This will not work. Parts of words may get replaced.
(text = "wordpad and winword are word processors,
text.Replace("word", "good word")

Marcus Riggs 13-Jul-18 22:51pm

WILL THIS REPLACE TEXT IN A TEXT FILE WITHOUT OPENING IT :)

#realJSOP 14-Jul-18 14:08pm

That’s impossible to do.

Toli Cuturicu · Answer 2 · 2010-07-20T04:59:00

Solution 1

Yes. Use REGular EXpressions!
Take a look at the Regex class.

For example something like this:

C#

string strFile = File.ReadAllText(@"c:\File1.txt");
strFile = Regex.Replace(strFile, @"\boldvalue\b", "newvalue");
File.WriteAllText(@"c:\File1.txt", strFile);

Posted 20-Jul-10 4:59am

Toli Cuturicu

Updated 21-Jul-10 12:10pm

v3

Comments

asjadazeez 21-Jul-10 3:39am

OK this does not work. reason i actually want that data to be writen on the file . My need is that i open a text file. search for a string, and this search i do using filestream and i search the string in each line, if the string is found in the line the, i need to replace that string with a new string. Regex give me methods to replace string but not in the file. Is there any way i can replace the string in the file.

Toli Cuturicu 21-Jul-10 18:10pm

I edited the answer a little. Look again, please.

#realJSOP 21-Jul-10 18:18pm

Why bother with Regex when the string object has a Replace method. You're using a sledge hammer to kill a fly.

Christian Graus 21-Jul-10 18:53pm

There is no way to change the text IN the file. You need to read the file in to memory, change it, and save it over the old file.

Sandeep Mewara 22-Jul-10 10:09am

You gave a comment to me here "http://www.codeproject.com/Answers/95939/Windows-Service.aspx#answer1"
Did you read the original question, the one i replied to before commenting?

Christian Graus · Answer 3 · 2010-07-21T12:55:00

Why don't you want to follow the only reasonable way to do this ? How is the computer supposed to know which values of 'oldvalue' are 'right' ? You'll need to write your own code to work that out, in which case you need to parse all the text, and make the changes in place, one at a time. There is no way to 'magically' change only the instances you want to, unless you can use regex to determine a rule that always applies to find just the ones you want to change.

How to replace words in a text file using C#

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