Shift text file rows by one deleting the first line

Question

how to Shift text file rows by one after deleting a particular line based on condition xyz=true for that particular line. I want to use C#.

 using (StreamWriter writer = new StreamWriter(file))
        {

            while ((line = rows[rowIndex++]) != null)
            {
            if( line contains xyz )// i know the logic to find this;
               {
                  delete this line and shift all below lines one up;
                 }
                 }
           }

The safe way of doing this is writing undeleted lines to a temporary file and, if everything worked, swap the temporary file with the original then delete the old file. [Here is an example](https://stackoverflow.com/questions/324670/). Not doing this can corrupt your file if you get an IO error partway through the change. — Dour High Arch, Feb 05 '18 at 17:12
`File.WriteAllLines(filePath, File.ReadAllLines(filePath).Where(line => !line.Contains("xyz")));` (this should work, but consider @DourHighArch comment about safely dealing with I/O errors) — Rufus L, Feb 05 '18 at 17:40

score 0 · Accepted Answer · answered Feb 05 '18 at 17:08

A simple way to do this for small files (files which can be completely loaded into memory) is to use File.ReadAllLines() to get a string[] of the lines. With this, you can loop through the array of strings and test each one to determine if it should be written to the new file or not.

A similar question came up recently here C# Delete line i text file if it is different than specific term

If you're writing the output to a new file, you don't need to worry about moving all the later lines up, removing the entire line will also remove the line ending characters.

Hope this helps

Shift text file rows by one deleting the first line

1 Answers1