Question

How can I get only the first line of multiline text using regular expressions?

        string test = @"just take this first line
        even there is 
        some more
        lines here";

        Match m = Regex.Match(test, "^", RegexOptions.Multiline);
        if (m.Success)
            Console.Write(m.Groups[0].Value);

Answer 1

string test = @"just take this first line
even there is 
some more
lines here";

Match m = Regex.Match(test, "^(.*)", RegexOptions.Multiline);
if (m.Success)
    Console.Write(m.Groups[0].Value);

. is often touted to match any character, while this isn’t totally true. . matches any character only if you use the RegexOptions.Singleline option. Without this option, it matches any character except for '\n' (end of line).

That said, a better option is likely to be:

string test = @"just take this first line
even there is 
some more
lines here";

string firstLine = test.Split(new string[] {Environment.NewLine}, StringSplitOptions.None)[0];

And better yet, is Brian Rasmussen’s version:

string firstline = test.Substring(0, test.IndexOf(Environment.NewLine));