Replacing strings in text files with C#
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  1. #1
    Join Date
    Apr 2009
    Posts
    1

    Post Replacing strings in text files with C#

    Upon searching for a way to replace occurences in text files, I only found methods that had to read the entire text file into the memory. These methods cannot be used for large files. That's why I have created this method:
    Code:
            /*
             * This method will replace all occurences of 'search' with 'replace' in the file with URI 'filepath' and backup the
             * original file to the 'backup' URI.
             * If 'ignoreEndsOfLine' is true, the method will also replace occurences that are split over 
             * multiple lines in the text. In that case, the file will also be rewritten on a single line.
             */
            public static void replaceInTextFile(string filepath, string search, string replace, bool ignoreEndsOfLine, string backup) {
                if (search == "" || search == null)
                {
                    throw new ArgumentException("'search' cannot be null or an empty string", "search");
                }
                StreamReader sr = new StreamReader(filepath);
                StreamWriter sw = new StreamWriter("TEMP" + filepath);
                char[] buffer = new char[search.Length];
                for (int i = 0; i < buffer.Length; i++) {
                    buffer[i] = (char)0;
                }
                while (sr.Peek() != -1)
                {
                    if (new string(buffer) == search)
                    {
                        sw.Write(replace);
                        for (int i = 0; i < buffer.Length; i++)
                        {
                            buffer[i] = (char)0;
                        }
                    }
                    else
                    {
                        if (buffer[0] != (char)0)
                        {    
                            sw.Write(buffer[0]);
                        }
                        for (int i = 0; i < buffer.Length; i++)
                        {
                            if (i < buffer.Length - 1)
                            {
                                buffer[i] = buffer[i + 1];
                            }
                            else
                            {
                                while (((char)sr.Peek() == (char)10 || (char)sr.Peek() == (char)13) && ignoreEndsOfLine)
                                {
                                    sr.Read();
                                }
                                buffer[i] = (char)sr.Read();
                            }
                        }
                    }
                }
                if (new string(buffer) == search)
                {
                    sw.Write(replace);
                }
                else
                {
                    for (int i = 0; i < buffer.Length; i++)
                    {
                        if (buffer[i] != (char)0)
                        {
                            sw.Write(buffer[i]);
                        }
                    }
                }
                sr.Close();
                sw.Close();
                FileInfo fi = new FileInfo("TEMP" + filepath);
                fi.Replace(filepath, backup, true);
            }
    I hope you can use and test this method of replacing strings in a text file. Please let me know when there are bugs in the method so that I can further develop it.
    Last edited by Shuja Ali; April 10th, 2009 at 08:34 AM. Reason: added code tags

  2. #2
    Join Date
    Jan 2002
    Location
    Scaro, UK
    Posts
    5,940

    Re: Replacing strings in text files with C#

    Please let me know when there are bugs in the method so that I can further develop it.
    Let me get this right : you want the forum to unit test your code ?

    I'd suggest you learn to do this by yourself : download NUnit to get started.

    Darwen.
    www.pinvoker.com - PInvoker - the .NET PInvoke Interface Exporter for C++ Dlls.

  3. #3
    Join Date
    Jun 2004
    Location
    Kashmir, India
    Posts
    6,808

    Re: Replacing strings in text files with C#

    Looks like it is a kind of tip that he wants to post. You should rather post it as a Tip on the Codegurus main page.

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