Removing consecutive blank rows from StringBuilder

Question

I have a Stringbuilder object that has been populated from a text file. How can I check the StringBuilder object for and remove consecutive "blank" lines.

i.e

Line 1: This is my text
Line 2:
Line 3: Another line after the 1st blank one
Line 4: 
Line 5:
Line 6: Next line after 2 blank lines

(Line numbers given as reference only)

The blank line on Line 2 is fine, but I would like to remove the duplicate blank line, on Line 5, and so on.

If for argument sake Line 6 would have also been a blank line, and a Line 7 had a value, I would like Blank Line 5 and Blank Line 6 removed, so that there would only be 1 blank line between the Line 3 and Line 7.

Thanks in advance.

Answer 1

Do you have to already have the file contents in a StringBuilder?

It would be nicer to be able to read line-by-line. Something like:

private IEnumerable<string> GetLinesFromFile(string fileName)
{
  using (var streamReader = new StreamReader(fileName))
  {
    string line = null;
    bool previousLineWasBlank = false;
    while ((line = streamReader.ReadLine()) != null)
    {
      if (!previousLineWasBlank && string.IsNullOrEmpty(line))
      {
        yield return line;
      }

      previousLineWasBlank = string.IsNullOrEmpty(line);
    }
  }
}

Now you can read in your text (which has had dupe blank lines removed) like this:

foreach (var line in GetLinesFromFile("myFile.txt"))
{
  Console.WriteLine(line);
}

Note: I'm only illustrating a technique here. There are other considerations: e.g. my iterator method holds the file open while the consumers are processing the foreach. This is nice and memory efficient (more so than reading into a string for example) as you are only dealing with one line at a time, but not ideal for files that take a long time to process.

Answer 2

Probably not very efficient, but it's easy.

while(sb.ToString().Contains(Environment.NewLine + Environment.NewLine))
{
    sb = sb.Replace(Environment.NewLine + Environment.NewLine, Environment.NewLine);
}