How to Find And Replace Text In A File With C

Question

My code so far  StreamReader reading   File OpenText  test txt    string str  while   str   reading ReadLine     null          if  str Contains  some text                      StreamWriter write   new StreamWriter  test txt                I know how to find the text  but I have no idea on how to replace the text in the file with my own

User · Answer

This code Worked for me   -   -------------------------------------------------------------------                               Create an instance of the Printer                            IPrinter printer   new Printer                                  ----------------------------------------------------------------------------                            String path         file browse path Text                               using  StreamReader sr   File OpenText path                               using  StreamReader sr   new System IO StreamReader path                                                               string fileLocMove                                   string newpath   Path GetDirectoryName path                                  fileLocMove   newpath           new prn                                        string text   File ReadAllText path                                     text  text Replace   lt REF gt    reference code Text                                     text    text Replace   lt ORANGE gt    orange name Text                                     text    text Replace   lt SIZE gt    size name Text                                     text    text Replace   lt INVOICE gt    invoiceName Text                                     text    text Replace   lt BINQTY gt    binQty Text                                     text   text Replace   lt DATED gt    dateName Text                                           File WriteAllText fileLocMove  text                                        Print the file                                printer PrintRawFile  Godex G500   fileLocMove   n                                     File WriteAllText  C   Users  Gunjan  Desktop  new prn   s

User · Answer

It is likely you will have to pull the text file into memory and then do the replacements  You will then have to overwrite the file using the method you clearly know about  So you would first      Read lines from source file  string   arr   File ReadAllLines file     YOu can then loop through and replace the text in the array     var writer   new StreamWriter GetFileName baseFolder  prefix  num    for  int i   0  i  lt  arr Length  i          string line   arr i       line Replace  match    new value        writer WriteLine line       this method gives you some control on the manipulations you can do  Or  you can merely do the replace in one line   File WriteAllText  test txt   text Replace  match    new value       I hope this helps

User · Answer

You need to write all the lines you read into the output file  even if you don t change them   Something like   using  var input   File OpenText  input txt    using  var output   new StreamWriter  output txt        string line    while  null     line   input ReadLine               optionally modify line       output WriteLine line           If you want to perform this operation in place then the easiest way is to use a temporary output file and at the end replace the input file with the output   File Delete  input txt    File Move  output txt    input txt       Trying to perform update operations in the middle of text file is rather hard to get right because always having the replacement the same length is hard given most encodings are variable width    EDIT  Rather than two file operations to replace the original file  better to use File Replace  input txt    output txt   null    See MSDN

User · Answer

i tend to use simple forward code as much as i can  below code worked fine with me   using System  using System IO  using System Text RegularExpressions        lt summary gt      Replaces text in a file       lt  summary gt       lt param name  filePath  gt Path of the text file  lt  param gt       lt param name  searchText  gt Text to search for  lt  param gt       lt param name  replaceText  gt Text to replace the search text  lt  param gt  static public void ReplaceInFile  string filePath  string searchText  string replaceText         StreamReader reader   new StreamReader  filePath        string content   reader ReadToEnd        reader Close         content   Regex Replace  content  searchText  replaceText         StreamWriter writer   new StreamWriter  filePath        writer Write  content        writer Close

User · Answer

This is how I did it with a large  50 GB  file   I tried 2 different ways  the first  reading the file into memory and using Regex Replace or String Replace  Then I appended the entire string to a temporary file   The first method works well for a few Regex replacements  but Regex Replace or String Replace could cause out of memory error if you do many replaces in a large file   The second is by reading the temp file line by line and manually building each line using StringBuilder and appending each processed line to the result file  This method was pretty fast               static void ProcessLargeFile             if  File Exists outFileName   File Delete outFileName            string text   File ReadAllText inputFileName  Encoding UTF8               EX 1 This opens entire file in memory and uses Replace and Regex Replace -- gt  might cause out of memory error          text   text Replace   lt  text gt                  text   Regex Replace text      lt ref     lt  ref  gt                  File WriteAllText outFileName  text                  EX 2 This reads file line by line           if  File Exists outFileName   File Delete outFileName            using  var sw   new StreamWriter outFileName                 using  var fs   File OpenRead inFileName           using  var sr   new StreamReader fs  Encoding UTF8     use UTF8 encoding or whatever encoding your file uses                       string line  newLine               while   line   sr ReadLine       null                                note  call your own replace function or use String Replace here                newLine   Util ReplaceDoubleBrackets line                  sw WriteLine newLine                                      public static string ReplaceDoubleBrackets string str                  note  this replaces the first occurrence of a word delimited by                  replace    with your own delimiter         if  str IndexOf        lt  0              return str           StringBuilder sb   new StringBuilder               this part gets the string to replace  put this in a loop if more than one occurrence  per line          int posStart   str IndexOf                int posEnd   str IndexOf                int length   posEnd - posStart                   code to replace with newstr           sb Append newstr            return sb ToString

User · Answer

You re going to have a hard time writing to the same file you re reading from  One quick way is to simply do this   File WriteAllText  test txt   File ReadAllText  test txt   Replace  some text   some other text       You can lay that out better with  string str   File ReadAllText  test txt    str   str Replace  some text   some other text    File WriteAllText  test txt   str

User · Answer

Read all file content  Make a replacement with String Replace  Write content back to file   string text   File ReadAllText  test txt    text   text Replace  some text    new value    File WriteAllText  test txt   text

[c#] How to Find And Replace Text In A File With C#

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