Regex Filter in C#

Question

I'm creating a sort of filter for a message, but running into some trouble with actually replacing parts of the word.

After looking over this question, I tried to do it almost exactly like they did. However, I want to work with multiple possible words to filter, and I want each to have a different thing to change to. A dictionary would seem to work perfectly for this. However, it does not work.

        Dictionary<string, string> filterWords = new Dictionary<string, string>
        {
            {"lol", "LAUGH OUT LOUD"},
            {"wtf", "WOW THAT'S FANTASTIC"},
        };

        foreach (KeyValuePair<string, string> word in filterWords)
        {
            Regex r = new Regex(@"\b" + word.Key + "\b");
            message = r.Replace(message, word.Value);
        }

I don't see anything really wrong with the code, but it doesn't actually replace any words, and I'm stumped as to how to fix it.

`I'm stumped as to how to fix it.` How to fix *what problem* ? — I4V, Jul 11 '13 at 19:25
Explain the problem! Theres no way to help you if you cant tell the real issue! — Fals, Jul 11 '13 at 19:27
At first I added it inside of the "" portion of the expression, so I was wrong to say that it did not work. @Chimoo — Linell, Jul 11 '13 at 19:37
great, so if it's fixed you should accept dasblinkenlight's answer — TimCodes.NET, Jul 11 '13 at 19:38
@Chimoo have to wait a certain time, I did it as soon as the time was up. — Linell, Jul 11 '13 at 19:39

Sergey Kalinichenko · Accepted Answer · 2013-07-11T19:32:19.153

6

The two problems that I see with this code is that it treats message case-sensitively, and that you missed the @ in front of the second "\b" literal, making "\b" a backspace, not an end-of-word marker.

Try replacing

Regex r = new Regex(@"\b" + word.Key + "\b");

with

Regex r = new Regex(@"\b" + word.Key + @"\b", RegexOptions.IgnoreCase);

the rest of your code should work fine.

You may want to optimize your code a little by per-compiling your regexes. In addition, since filterWords is not really a Dictionary, you may want to use List<Tuple<Regex,string>>.

edited Jul 11 '13 at 19:32

answered Jul 11 '13 at 19:26

Sergey Kalinichenko

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Usually, you are lucky when you forget to escape a character and get the unkown escape sequence compilation error, but if you choose one of these: http://blogs.msdn.com/b/csharpfaq/archive/2004/03/12/what-character-escape-sequences-are-available.aspx, it will compile just fine – Gray Jul 11 '13 at 19:29
1

`@"\\b"` and `"\\b"` are different, corresponding to `\\b` and `\b` respectively. I think you want `@"\b"` or `"\\b"`, which parse to `\b`, which parses to regex's word boundary. – Tim S. Jul 11 '13 at 19:30

Regex Filter in C#

1 Answers1