Best way to split string into lines

Question

How do you split multi-line string into lines?

I know this way

var result = input.Split("\n\r".ToCharArray(), StringSplitOptions.RemoveEmptyEntries);

looks a bit ugly and loses empty lines. Is there a better solution?

Answer 1

• If it looks ugly, just remove the unnecessary ToCharArray call.

• If you want to split by either \n or \r , you've got two options:

  • Use an array literal – but this will give you empty lines for Windows-style line endings \r\n :

     var result = text.Split(new [] { '\r', '\n' });

  • Use a regular expression, as indicated by Bart:

     var result = Regex.Split(text, "\r\n|\r|\n");

• If you want to preserve empty lines, why do you explicitly tell C# to throw them away? ( StringSplitOptions parameter) – use StringSplitOptions.None instead.

Answer 2

using (StringReader sr = new StringReader(text)) {
    string line;
    while ((line = sr.ReadLine()) != null) {
        // do something
    }
}

Answer 3

Update: See here for an alternative/async solution.

---

This works great and is faster than Regex:

input.Split(new[] {"\r\n", "\r", "\n"}, StringSplitOptions.None)

It is important to have "\r\n" first in the array so that it's taken as one line break. The above gives the same results as either of these Regex solutions:

Regex.Split(input, "\r\n|\r|\n")

Regex.Split(input, "\r?\n|\r")

Except that Regex turns out to be about 10 times slower. Here's my test:

Action<Action> measure = (Action func) => {
    var start = DateTime.Now;
    for (int i = 0; i < 100000; i++) {
        func();
    }
    var duration = DateTime.Now - start;
    Console.WriteLine(duration);
};

var input = "";
for (int i = 0; i < 100; i++)
{
    input += "1 \r2\r\n3\n4\n\r5 \r\n\r\n 6\r7\r 8\r\n";
}

measure(() =>
    input.Split(new[] {"\r\n", "\r", "\n"}, StringSplitOptions.None)
);

measure(() =>
    Regex.Split(input, "\r\n|\r|\n")
);

measure(() =>
    Regex.Split(input, "\r?\n|\r")
);

Output:

00:00:03.8527616

00:00:31.8017726

00:00:32.5557128

and here's the Extension Method:

public static class StringExtensionMethods
{
    public static IEnumerable<string> GetLines(this string str, bool removeEmptyLines = false)
    {
        return str.Split(new[] { "\r\n", "\r", "\n" },
            removeEmptyLines ? StringSplitOptions.RemoveEmptyEntries : StringSplitOptions.None);
    }
}

Usage:

input.GetLines()      // keeps empty lines

input.GetLines(true)  // removes empty lines

Answer 4

You could use Regex.Split:

string[] tokens = Regex.Split(input, @"\r?\n|\r");

Edit: added |\r to account for (older) Mac line terminators.

Answer 5

如果您想保留空行，只需删除 StringSplitOptions。

var result = input.Split(System.Environment.NewLine.ToCharArray());

Answer 6

string[] lines = input.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);

Answer 7

I had this other answer but this one, based on Jack's answer , is significantly faster might be preferred since it works asynchronously, although slightly slower.

public static class StringExtensionMethods
{
    public static IEnumerable<string> GetLines(this string str, bool removeEmptyLines = false)
    {
        using (var sr = new StringReader(str))
        {
            string line;
            while ((line = sr.ReadLine()) != null)
            {
                if (removeEmptyLines && String.IsNullOrWhiteSpace(line))
                {
                    continue;
                }
                yield return line;
            }
        }
    }
}

Usage:

input.GetLines()      // keeps empty lines

input.GetLines(true)  // removes empty lines

Test:

Action<Action> measure = (Action func) =>
{
    var start = DateTime.Now;
    for (int i = 0; i < 100000; i++)
    {
        func();
    }
    var duration = DateTime.Now - start;
    Console.WriteLine(duration);
};

var input = "";
for (int i = 0; i < 100; i++)
{
    input += "1 \r2\r\n3\n4\n\r5 \r\n\r\n 6\r7\r 8\r\n";
}

measure(() =>
    input.Split(new[] { "\r\n", "\r", "\n" }, StringSplitOptions.None)
);

measure(() =>
    input.GetLines()
);

measure(() =>
    input.GetLines().ToList()
);

Output:

00:00:03.9603894

00:00:00.0029996

00:00:04.8221971

Answer 8

Slightly twisted, but an iterator block to do it:

public static IEnumerable<string> Lines(this string Text)
{
    int cIndex = 0;
    int nIndex;
    while ((nIndex = Text.IndexOf(Environment.NewLine, cIndex + 1)) != -1)
    {
        int sIndex = (cIndex == 0 ? 0 : cIndex + 1);
        yield return Text.Substring(sIndex, nIndex - sIndex);
        cIndex = nIndex;
    }
    yield return Text.Substring(cIndex + 1);
}

You can then call:

var result = input.Lines().ToArray();

Answer 9

["

It's tricky to handle mixed<\/em><\/strong> line endings properly.<\/i>

Answer 10

    private string[] GetLines(string text)
    {

        List<string> lines = new List<string>();
        using (MemoryStream ms = new MemoryStream())
        {
            StreamWriter sw = new StreamWriter(ms);
            sw.Write(text);
            sw.Flush();

            ms.Position = 0;

            string line;

            using (StreamReader sr = new StreamReader(ms))
            {
                while ((line = sr.ReadLine()) != null)
                {
                    lines.Add(line);
                }
            }
            sw.Close();
        }



        return lines.ToArray();
    }

Answer 11

Split a string into lines without any allocation.

public static LineEnumerator GetLines(this string text) {
    return new LineEnumerator( text.AsSpan() );
}

internal ref struct LineEnumerator {

    private ReadOnlySpan<char> Text { get; set; }
    public ReadOnlySpan<char> Current { get; private set; }

    public LineEnumerator(ReadOnlySpan<char> text) {
        Text = text;
        Current = default;
    }

    public LineEnumerator GetEnumerator() {
        return this;
    }

    public bool MoveNext() {
        if (Text.IsEmpty) return false;

        var index = Text.IndexOf( '\n' ); // \r\n or \n
        if (index != -1) {
            Current = Text.Slice( 0, index + 1 );
            Text = Text.Slice( index + 1 );
            return true;
        } else {
            Current = Text;
            Text = ReadOnlySpan<char>.Empty;
            return true;
        }
    }


}

Answer 12

late to the party, but I've been using a simple collection of extension methods for just that, which leverages TextReader.ReadLine() :

public static class StringReadLinesExtension
{
    public static IEnumerable<string> GetLines(this string text) => GetLines(new StringReader(text));
    public static IEnumerable<string> GetLines(this Stream stm) => GetLines(new StreamReader(stm));
    public static IEnumerable<string> GetLines(this TextReader reader) {
        string line;
        while ((line = reader.ReadLine()) != null)
            yield return line;
        reader.Dispose();
        yield break;
    }
}

Using the code is really trivial:

// If you have the text as a string...
var text = "Line 1\r\nLine 2\r\nLine 3";
foreach (var line in text.GetLines())
    Console.WriteLine(line);
// You can also use streams like
var fileStm = File.OpenRead("c:\tests\file.txt");
foreach(var line in fileStm.GetLines())
    Console.WriteLine(line);

Hope this helps someone out there.