Replace text which contain line breaks without dropping them

Question

We have a text which goes like this ..

This is text
                i want
                to keep
                    but
                Replace this sentence
                because i dont like it.

Now i want to replace this sentence Replace this sentence because i dont like it.

Of course going like this

text = text.Replace(@"Replace this sentence because i dont like it.", "");

Wont solve my problem. I can't drop line breaks and replace them with one line.

My output should be

This is text
                i want
                to keep
                    but

Please keep in mind there is a lot variations and line breaks for sentence i don't like.

I.E it may go like

Replace this 
sentence
                    because i dont like it.

or

Some text before. Replace this 
    sentence
                        because i dont like it.

Olivier Jacot-Descombes · Accepted Answer · 2019-11-02T21:40:35.150

You can use Regex to find any kind of whitespace. This includes regular spaces but also carriage returns and linefeeds as well as tabulators or half-spaces and so on.

string input = @"This is text
    i want
    to keep
        but
    Replace this sentence
    because i dont like it.";

string dontLike = @"Replace this sentence because i dont like it.";
string pattern = Regex.Escape(dontLike).Replace(@"\ ", @"\s+");

Console.WriteLine("Pattern:");
Console.WriteLine(pattern);

string clean = Regex.Replace(input, pattern, "");

Console.WriteLine();
Console.WriteLine("Result:");
Console.WriteLine(clean);
Console.ReadKey();

Output:

Pattern:
Replace\s+this\s+sentence\s+because\s+i\s+dont\s+like\s+it\.

Result:
This is text
                i want
                to keep
                    but

Regex.Escape escapes any character that would otherwise have a special meaning in Regex. E.g., the period "." means "any number of repetitions". It also replaces the spaces " " with @"\ ". We in turn replace @"\ " in the search pattern by @"\s+". \s+ in Regex means "one or more white spaces".

score 1 · Answer 2 · answered Nov 02 '19 at 19:03

Use regex to match "any whitespace" instead of just space in your search string. Roughly

escape search string to be safe for regex -Escape Special Character in Regex
replace spaces with "\s+" (reference)
run regex matching multiple lines - Multiline regular expression in C#

score 1 · Answer 3 · answered Nov 02 '19 at 19:44

Or, use LINQ to accomplish this:

var text = "Drones " + Environment.NewLine + "are great to fly, " + Environment.NewLine + "yes, very fun!";
var textToReplace = "Drones are great".Split(" ").ToList();
textToReplace.ForEach(f => text = text.Replace(f, ""));

Output:

to fly, 

yes, very fun!

Whatever method you choose, you are going to deal with extra line breaks, too many spaces and other formatting issues... Good luck!

score 0 · Answer 4 · answered Nov 02 '19 at 19:55

You can use something like this, if output format of string is optional here:

using System;
using System.Text.RegularExpressions;

public class Program
{
    public static void Main()
    {
        string textToReplace = @"Replace this sentence because i dont like it.";
        string text = @"This is text
                i want
                to keep
                    but
                Replace this sentence
                because i dont like it.";

        text = Regex.Replace(text, @"\s+", " ", RegexOptions.Multiline);
        text = text.Replace(textToReplace, string.Empty);
        Console.WriteLine(text);
    }
}

Output:

"This is text i want to keep but"

Replace text which contain line breaks without dropping them

4 Answers4