如何编写从开始到出现新行匹配字符串的正则表达式？

Question

how to match string from beginning to first new line feed.

Example if TextBox1.Text value is

'START: Milestone One\\r\\nFirst milestone is achieved in a week.'

Here is what I am trying:-

TextBox1.Text = Regex.Replace(TestBox1.Text, @"START: \w+\s?", "");

This Regex is finding first word only therefore replacing 'START: MileStone' with string.empty but leaving 'One' there.

I need to replace everything (including newline feed) before first newline feed.

Answer 1

You do not need a regex for that, just use IndexOf('\\n') + 1 :

var t = "START: Milestone One\r\nFirst milestone is achieved in a week.";
Console.WriteLine(t.Substring(t.IndexOf('\n') + 1).Trim());

See IDEONE demo

Result: First milestone is achieved in a week.

A regex will not be efficient here, but you can check it for yourself:

var text = Regex.Replace(t, @"(?>.+\r?\n)\s*", string.Empty);

See another demo

Answer 2

You can also use LINQ:

string str = "START: Milestone One\r\nFirst milestone is achieved in a week.";

string newStr = String.Join("", str.SkipWhile(c => c != '\n').Skip(1));

Console.WriteLine(newStr); // First milestone is achieved in a week.

To check if the input string is null or contains any \\n :

string newStr = (str?.Any(c => c == '\n')).GetValueOrDefault() ? String.Join("", str.SkipWhile(c => c != '\n').Skip(1)) : str;

Answer 3

I don't know if your anything like me but maybe you are practicing Regex and want to know how to make it happen with it. I'm very new at coding but I took your example and this is how I would make it happen.

    private void button1_Click(object sender, EventArgs e)
    {
        string test = "START: Milestone One\r\nFirst milestone is achieved in a week.";

        string final = Regex.Replace(test, ".*\\n", "START: ").ToString();
        MessageBox.Show(final); // START: First milestone is achieved in a week.
    }

Not sure if that helps your or not but thought I would try. Have a nice day!

Answer 4

Just fixing your regex:

[\w\s]+\n

you might need to play with \\n and \\ra bit. [\\w\\s] is equivalent to . so .*\\n will do the job as well

Yours didn't work as you stopped at first whitespace, while you want to replace any word or whitespace until the linefeed, as far as I can understand.