C# Regex Issue "unrecognized escape sequence"

Question

I have an issue with the regular expressions I'm using but don't know how to continue with them. I get the error "unrecognized escape sequence".

I am trying to list out all files that could have a phone number in the formats listed in the code below

static void Main(string[] args)

    {
        //string pattern1 = "xxx-xxx-xxxx";
        //string pattern2 = "xxx.xxx.xxxx";
        //string pattern3 = "(xxx) xxx-xxxx";

        string[] fileEntries = Directory.GetFiles(@"C:\BTISTestDir");

        foreach (string filename in fileEntries)
        {
            StreamReader reader = new StreamReader(filename);
            string content = reader.ReadToEnd();
            reader.Close();

            string regexPattern1 = "^(\d{3}\.){2}\d{4}$";
            string regexPattern2 = "^((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}$";

            if(Regex.IsMatch(content, regexPattern1))
                Console.WriteLine("File found: " + filename);
            if(Regex.IsMatch(content, regexPattern2))
                Console.WriteLine("File found: " + filename);
        }

        Console.WriteLine(Environment.NewLine + "Finished");
        Console.ReadLine();
    }

Any help is much appreciated.

Save yourself some trouble and use (?:\(\d{3}\)|\d{3})[\s\.-]\d{3}[\.-]\d{4} — Brad Christie
– Brad Christie, Commented May 27, 2011 at 16:42
possible duplicate of Unrecognized escape sequence for path string containing backslashes — JasonMArcher
– JasonMArcher, Commented Feb 5, 2015 at 0:06

Mamun · Accepted Answer · 2019-06-17 05:38:31Z

90

Use @ to make the strings no longer use the escape character \:

string regexPattern1 = @"^(\d{3}\.){2}\d{4}$";
string regexPattern2 = @"^((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}$";

As a side note, I think you want the two ifs at the end to be a single if with an or (||) between the two conditions.

edited Jun 17, 2019 at 5:38

Mamun

69k9 gold badges51 silver badges62 bronze badges

answered May 27, 2011 at 16:36

Blindy

68k10 gold badges96 silver badges141 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Brad Christie Over a year ago

I could be wrong, and this may be a new format, but a string literal needs the @ before the quote, not the variable name.

leppie Over a year ago

@Blindy: You can be lucky there is no changelog for the answer yet ;p

Blindy Over a year ago

Well, for what it's worth, @identifier is valid C# syntax <.<

Blake Rogers Over a year ago

@Blindly Thanks. Also for the thought of combining the if statements. Now it accepts my regex but i'm not getting any files returned and I know that it should be returning stuff... weird. I made a text file with those patterns in it.

Blindy Over a year ago

@Blake, give me an example of the file names you made. They should be like 123.456.1234 with nothing else around them.

|

user2074102 · Accepted Answer · 2013-12-18 14:59:40Z

9

Add an additional '\' to unescape the escape. When it's processed it will then be interpreted in the manner you intended.

answered Dec 18, 2013 at 14:59

user2074102

1 Comment

AbeyMarquez Over a year ago

+1 because this works beautifully in the rare case that you have to escape a double quote (") character. (ex. \\\")

King_DuckZ · Accepted Answer · 2011-05-27 16:40:56Z

5

The problem is not the regex, but the string. Before compiling it to a regex with the call to IsMatch(), the text you enter is still a normal string and it must obey the language rules.

\d in your language is not a recognized escape sequence, hence the error. You can either double backslashes (\ is the escape sequence to get a ) or, as Blindy pointed out, you can prefix your constant strings with a @, telling the compiler that it should not try to interpret anything looking like an escape sequence to it.

answered May 27, 2011 at 16:40

King_DuckZ

2381 silver badge6 bronze badges

Collectives™ on Stack Overflow

C# Regex Issue "unrecognized escape sequence"

3 Answers 3

6 Comments

1 Comment

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

6 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related