How do I remove blank lines from text File in c#.net

I want to remove blank lines from my file, foe that I am using code below.

 private void ReadFile(string Address)
{

    var tempFileName = Path.GetTempFileName();
    try
    {
        //using (var streamReader = new StreamReader(Server.MapPath("~/Images/") + FileName))
        using (var streamReader = new StreamReader(Address))
        using (var streamWriter = new StreamWriter(tempFileName))
        {
            string line;
            while ((line = streamReader.ReadLine()) != null)
            {
                if (!string.IsNullOrWhiteSpace(line))
                    streamWriter.WriteLine(line);
            }
        }
        File.Copy(tempFileName, Address, true);
    }
    finally
    {
        File.Delete(tempFileName);
    }
    Response.Write("Completed");
}

But the problem is my file is too large (8 lac lines ) so its taking lot of time. So is there any other way to do it faster?

Jon Skeet
people
quotationmark

The best solution may well depend on the disk type - SSDs and spinning rust behave differently. Your current approach has the advantage over Steve's answer of being able to do processing (such as encoding text data back as binary) while data is still coming off the disk. (With buffering and background IO, there's a lot of potential asynchrony here.) It's definitely worth trying both approaches. (Obviously your approach uses less memory, too.)

However, there's one aspect of your code which is definitely suboptimal: creating a copy of the results. You don't need to do that. You can use file moves instead which are a lot more efficient, assuming they're all in the same drive. To make sure you don't lose data, you can do two moves and a delete:

  • Move the old file to a backup filename
  • Move the new file to the old filename
  • Delete the backup filename

It looks like this is what File.Replace does for you, which makes it considerably simpler, and also preserves the original metadata.

If something goes wrong after the first move, you're left without the "proper" file from either old or new, but you can detect that and use the backup filename to read next time.

Of course, if this is meant to happen as part of a web request, you may want to do all the processing in a background task - processing 800,000 lines of text is likely to take longer than you really want a web request to take...

people

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