Replacing strings in text files with C#

[kevinvl123]

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:

        /*
         * 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.

[darwen]

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.

[Shuja Ali]

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.