C#: What's the best way to delete empty lines from a multiline string?

Question

In C# what's the best way to remove blank lines i.e., lines that contain only whitespace from a string? I'm happy to use a Regex if that's the best solution.

EDIT: I should add I'm using .NET 2.0.

Answer 1

string corrected = 
    System.Text.RegularExpressions.Regex.Replace(input, @"\n+", "\n");

Answer 2

Using LINQ:

var result = string.Join("\r\n",
                 multilineString.Split(new string[] { "\r\n" }, ...None)
                                .Where(s => !string.IsNullOrWhitespace(s)));

If you're dealing with large inputs and/or inconsistent line endings you should use a StringReader and do the above old-school with a foreach loop instead.

Answer 3

char[] delimiters = new char[] { '\r', '\n' };
string[] lines = value.Split(delimiters, StringSplitOptions.RemoveEmptyEntries);
string result = string.Join(Environment.NewLine, lines)

Answer 4

off the top of my head...

string fixed = Regex.Replace(input, "\s*(\n)","$1");

turns this:

fdasdf
asdf
[tabs]

[spaces]  

asdf

into this:

fdasdf
asdf
asdf

Answer 5

string outputString;
using (StringReader reader = new StringReader(originalString)
using (StringWriter writer = new StringWriter())
{
    string line;
    while((line = reader.ReadLine()) != null)
    {
        if (line.Trim().Length > 0)
            writer.WriteLine(line);
    }
    outputString = writer.ToString();
}

Answer 6

If you want to remove lines containing any whitespace (tabs, spaces), try:

string fix = Regex.Replace(original, @"^\s*$\n", string.Empty, RegexOptions.Multiline);

Answer 7

Here's another option: use the StringReader class. Advantages: one pass over the string, creates no intermediate arrays.

public static string RemoveEmptyLines(this string text) {
    var builder = new StringBuilder();

    using (var reader = new StringReader(text)) {
        while (reader.Peek() != -1) {
            string line = reader.ReadLine();
            if (!string.IsNullOrWhiteSpace(line))
                builder.AppendLine(line);
        }
    }

    return builder.ToString();
}

Note: the IsNullOrWhiteSpace method is new in .NET 4.0. If you don't have that, it's trivial to write on your own:

public static bool IsNullOrWhiteSpace(string text) {
    return string.IsNullOrEmpty(text) || text.Trim().Length < 1;
}

Answer 8

I'll go with:

  public static string RemoveEmptyLines(string value) {
    using (StringReader reader = new StringReader(yourstring)) {
      StringBuilder builder = new StringBuilder();
      string line;
      while ((line = reader.ReadLine()) != null) {
        if (line.Trim().Length > 0)
          builder.AppendLine(line);
      }
      return builder.ToString();
    }
  }

Answer 9

Try this.

string s = "Test1" + Environment.NewLine + Environment.NewLine + "Test 2";
Console.WriteLine(s);

string result = s.Replace(Environment.NewLine, String.Empty);
Console.WriteLine(result);

Answer 10

s = Regex.Replace(s, @"^[^\n\S]*\n", "");

[^\n\S] matches any character that's not a linefeed or a non-whitespace character--so, any whitespace character except \n. But most likely the only characters you have to worry about are space, tab and carriage return, so this should work too:

s = Regex.Replace(s, @"^[ \t\r]*\n", "");

And if you want it to catch the last line, without a final linefeed:

s = Regex.Replace(s, @"^[ \t\r]*\n?", "");